Author name code: kurokawa ADS astronomy entries on 2022-09-14 author:"Kurokawa, Hiroki" ------------------------------------------------------------------------ Title: Approach to the Mapping of Water Environment on Present Mars - Validation of Possible Water Vapor Emission from Recurring Slope Lineae Using a GCM Authors: Kuroda, T.; Kurokawa, H.; Aoki, S.; Nakagawa, H.; Kobayashi, M. Bibcode: 2022mamo.conf.3515K Altcode: No abstract at ADS Title: The Origin of Earth's Mantle Nitrogen: Primordial or Early Biogeochemical Cycling? Authors: Kurokawa, H.; Laneuville, M.; Li, Y.; Zhang, N.; Fujii, Y.; Sakuraba, H.; Houser, C.; Cleaves, H. J. Bibcode: 2022GGG....2310295K Altcode: 2022arXiv220414002K Earth's mantle nitrogen (N) content is comparable to that found in its N-rich atmosphere. Mantle N has been proposed to be primordial or sourced by later subduction, yet its origin has not been elucidated. Here we model N partitioning during the magma ocean stage following planet formation and the subsequent cycling between the surface and mantle over Earth history using argon (Ar) and N isotopes as tracers. The partitioning model, constrained by Ar, shows that only about 10% of the total N content can be trapped in the solidified mantle due to N's low solubility in magma and low partitioning coefficients in minerals in oxidized conditions supported from geophysical and geochemical studies. A possible solution for the primordial origin is that Earth had about 10 times more N at the time of magma ocean solidification. We show that the excess N could be removed by impact erosion during late accretion. The cycling model, constrained by N isotopes, shows that mantle N can originate from efficient N subduction, if the sedimentary N burial rate on early Earth is comparable to that of modern Earth. Such a high N burial rate requires biotic processing. Finally, our model provides a methodology to distinguish the two possible origins with future analysis of the surface and mantle N isotope record. Title: Mars Atmospheric Neon Probes Mantle Volatile Content and Early Surface Environment Authors: Kurokawa, H.; Sugita, S.; Yoshida, T.; Miura, Y. N.; Cho, Y.; Kumagai, H.; Leblanc, F.; Terada, N.; Nakagawa, H.; Kasahara, S.; Yoshioka, K.; Iwata, N.; Saito, Y. Bibcode: 2022LPICo2678.1722K Altcode: Mars' atmospheric Ne abundance suggests volatile-rich interior. Determination of its isotopic ratio is crucial to elucidate Mars' accretion and early evolution. Title: Speciation of Sulfur in Carbonates in a 4.1-Billion-Year-Old Martian Meteorite Authors: Kajitani, I.; Nakada, R.; Koike, M.; Tanabe, G.; Usui, T.; Matsu'ura, F.; Fukushi, K.; Kurokawa, H.; Yokoyama, T. Bibcode: 2022LPICo2678.1863K Altcode: XANES analysis of carbonates in ALH 84001 showed peaks corresponding to S(Ⅵ) at all analytical points and the S(Ⅵ) exists as carbonate associated sulfate (CAS). Title: Distant Formation and Water-Rock Differentiation of Large C-Complex Asteroids Authors: Kurokawa, H.; Shibuya, T.; Sekine, Y.; Ehlmann, B. L.; Usui, F.; Kikuchi, S.; Yoda, M. Bibcode: 2022LPICo2678.1676K Altcode: Spectral identification of ammoniated minerals and water-rock reaction modeling suggest distant formation and differentiation of large C-complex asteroids. Title: Distant Formation and Differentiation of Outer Main Belt Asteroids and Carbonaceous Chondrite Parent Bodies Authors: Kurokawa, H.; Shibuya, T.; Sekine, Y.; Ehlmann, B. L.; Usui, F.; Kikuchi, S.; Yoda, M. Bibcode: 2022AGUA....300568K Altcode: 2021arXiv211210284K Volatile compositions of asteroids provide information on the Solar System history and the origins of Earth's volatiles. Visible to near-infrared observations at wavelengths of <2.5 µm have suggested a genetic link between outer main belt asteroids located at 2.5-4 au and carbonaceous chondrite meteorites (CCs) that show isotopic similarities to volatile elements on Earth. However, recent longer wavelength data for large outer main belt asteroids show 3.1 μm absorption features of ammoniated phyllosilicates that are absent in CCs and cannot easily form from materials stable at those present distances. Here, by combining data collected by the AKARI space telescope and hydrological, geochemical, and spectral models of water-rock reactions, we show that the surface materials of asteroids having 3.1 μm absorption features and CCs can originate from different regions of a single, water-rock-differentiated parent body. Ammoniated phyllosilicates form within the water-rich mantles of the differentiated bodies containing NH3 and CO2 under high water-rock ratios (>4) and low temperatures (<70°C). CCs can originate from the rock-dominated cores, that are likely to be preferentially sampled as meteorites by disruption and transport processes. Our results suggest that multiple large main belt asteroids formed beyond the NH3 and CO2 snow lines (currently >10 au) and could be transported to their current locations. Earth's high hydrogen to carbon ratio may be explained by accretion of these water-rich progenitors. Title: Partitioning and atmospheric loss of major volatile elements on accreting Venus: Implications for the early runaway greenhouse state Authors: Sakuraba, H.; Kurokawa, H. Bibcode: 2020AGUFMP018...07S Altcode: Due to limited information, the climate of early Venus has been poorly understood. Venus might have been in the runaway greenhouse state since its formation, in which water forms a steam atmosphere (e.g., Goldblatt et al., 2013, Hamano et al., 2013). On the other hand, a habitable climate with liquid oceans has been also suggested as another possibility (e.g., Way and Del Genio, 2020).

Here we show that the distinct ratios of the major volatile elements, carbon and nitrogen, on Venus and Earth suggest the early runaway greenhouse scenario. Present-day Venusian volatile budget shows a deficient in water by orders of magnitude and low C/N ratio by a factor of ~4 compared to the bulk silicate Earth (e.g., Catling & Kasting, 2017, Bergin et al., 2015). Hydrodynamic escape from the primordial atmosphere is thought to have contributed to the water loss, but another mechanism is needed to explain the C/N fractionation.

In this study, we adapted a numerical model of element partitioning between the atmosphere, crust, mantle (magma ocean), and core as well as impact-induced atmospheric escape (Sakuraba et al., 2019; Sakuraba et al., submitted) to accreting Venus. We estimated the final volatile inventories for both cases of the runaway greenhouse state and of Earth-like habitable condition. In the former case, all volatile species on the surface were assumed to be partitioned into the atmosphere. In the latter case, water and carbon were assumed to be partitioned into liquid oceans and sedimentary carbonates, respectively, after the magma ocean solidification.

Finally, Venusian low C/N ratio was reproduced in the runaway greenhouse case, while Earth-like high C/N ratio was obtained in the habitable case. In the former case, both C and N were mainly partitioned to the atmosphere through the accretion due to their low solubilities into the magma ocean and lack of surface reservoirs after the magma ocean solidification. Therefore, the impact-induced atmospheric erosion removed them equally. In contrast, preferential loss of atmospheric N as a result of C capture in carbonates elevated the C/N ratio in the latter case. As a conclusion, we propose that the combination of the runaway greenhouse state and the impact-induced atmospheric escape on early Venus are required to explain the present-day volatile abundances. Title: A Probabilistic Approach to Determination of Ceres' Average Surface Composition From Dawn Visible-Infrared Mapping Spectrometer and Gamma Ray and Neutron Detector Data Authors: Kurokawa, H.; Ehlmann, B. L.; De Sanctis, M. C.; Lapôtre, M. G. A.; Usui, T.; Stein, N. T.; Prettyman, T. H.; Raponi, A.; Ciarniello, M. Bibcode: 2020JGRE..12506606K Altcode: The Visible-Infrared Mapping Spectrometer (VIR) on board the Dawn spacecraft revealed that aqueous secondary minerals—Mg-phyllosilicates, NH4-bearing phases, and Mg/Ca carbonates—are ubiquitous on Ceres. Ceres' low reflectance requires dark phases, which were assumed to be amorphous carbon and/or magnetite (∼80 wt.%). In contrast, the Gamma Ray and Neutron Detector (GRaND) constrained the abundances of C (8-14 wt.%) and Fe (15-17 wt.%). Here, we reconcile the VIR-derived mineral composition with the GRaND-derived elemental composition. First, we model mineral abundances from VIR data, including either meteorite-derived insoluble organic matter (IOM), amorphous carbon, magnetite, or combination as the darkening agent and provide statistically rigorous error bars from a Bayesian algorithm combined with a radiative-transfer model. Elemental abundances of C and Fe are much higher than is suggested by the GRaND observations for all models satisfying VIR data. We then show that radiative transfer modeling predicts higher reflectance from a carbonaceous chondrite of known composition than its measured reflectance. Consequently, our second models use multiple carbonaceous chondrite endmembers, allowing for the possibility that their specific textures or minerals other than carbon or magnetite act as darkening agents, including sulfides and tochilinite. Unmixing models with carbonaceous chondrites eliminate the discrepancy in elemental abundances of C and Fe. Ceres' average reflectance spectrum and elemental abundances are best reproduced by carbonaceous-chondrite-like materials (40-70 wt.%), IOM or amorphous carbon (10 wt.%), magnetite (3-8 wt.%), serpentine (10-25 wt.%), carbonates (4-12 wt.%), and NH4-bearing phyllosilicates (1-11 wt.%). Title: A probabilistic approach to determination of Ceres' average surface composition from Dawn VIR and GRaND data Authors: Kurokawa, H.; Ehlmann, B. L.; De Sanctis, M. C.; Lapôtre, M. G. A.; Usui, T.; Stein, N. T.; Prettyman, T. H.; Raponi, A.; Ciarniello, M. Bibcode: 2020arXiv201100157K Altcode: The Visible-Infrared Mapping Spectrometer (VIR) on board the Dawn spacecraft revealed that aqueous secondary minerals -- Mg-phyllosilicates, NH4-bearing phases, and Mg/Ca carbonates -- are ubiquitous on Ceres. Ceres' low reflectance requires dark phases, which were assumed to be amorphous carbon and/or magnetite (~80 wt.%). In contrast, the Gamma Ray and Neutron Detector (GRaND) constrained the abundances of C (8-14 wt.%) and Fe (15-17 wt.%). Here, we reconcile the VIR-derived mineral composition with the GRaND-derived elemental composition. First, we model mineral abundances from VIR data, including either meteorite-derived insoluble organic matter, amorphous carbon, magnetite, or combination as the darkening agent and provide statistically rigorous error bars from a Bayesian algorithm combined with a radiative-transfer model. Elemental abundances of C and Fe are much higher than is suggested by the GRaND observations for all models satisfying VIR data. We then show that radiative transfer modeling predicts higher reflectance from a carbonaceous chondrite of known composition than its measured reflectance. Consequently, our second models use multiple carbonaceous chondrite endmembers, allowing for the possibility that their specific textures or minerals other than carbon or magnetite act as darkening agents, including sulfides and tochilinite. Unmixing models with carbonaceous chondrites eliminate the discrepancy in elemental abundances of C and Fe. Ceres' average reflectance spectrum and elemental abundances are best reproduced by carbonaceous-chondrite-like materials (40-70 wt.%), IOM or amorphous carbon (10 wt.%), magnetite (3-8 wt.%), serpentine (10-25 wt.%), carbonates (4-12 wt.%), and NH4-bearing phyllosilicates (1-11 wt.%). Title: Proto-atmosphere Accretion on Eccentric Planets and its Impact on Planet Formation Authors: Mai, C.; Desch, S.; Kuiper, R.; Kurokawa, H.; Kuwahara, A.; Marleau, G. Bibcode: 2020AAS...23522405M Altcode: Protoplanets are believed to form before gas dissipates in the protoplanetary disk and are likely to capture proto-atmospheres from the nebula gas. Such hydrogen-rich atmospheres have been detected and characterized in exoplanetary systems (e.g. low-density super-Earths and mini-Neptunes). The accretion process and the structure of the proto-atmosphere is subject to the disk environment such as the evaporation of nebula gas, the eccentricity of the planet's orbit and the planet mass, etc. A gaseous envelope could also greatly change the behaviors of solids in the proximity of a protoplanet and affect the planet formation processes. We used the hydrodynamics code PLUTO and the radiation transport module MAKEMAKE to model the accretion event of H2-dominated atmospheres. We established a 2-D radiative accretion model with sophisticated opacity treatment to simulate protoplanets capturing atmospheres on eccentric orbits. The solutions reveal recycling behaviors of gas flow in a planetary bow shock structure. We found that a supersonic environment turns out to be favorable for planets to keep an early stable atmosphere, rather than harmful. The orbital evolution of the planet can also insert a forced oscillation on the atmosphere properties. Based on the hydrodynamics solutions, we have been computing the dynamics of incoming pebbles subject to the planet's gravity and aerodynamic drag forces. We have been looking into how the accretion efficiency of different sized pebbles on terrestrial planets is affected by the proto-atmospheres. When planets are on eccentric orbits, the trajectories of incoming solids are deflected in the bow shock, but the recycling gas could also bring back solids for accretion behind the planet. Updated results will be presented in the meeting. Our study explores and provides important insights into the impacts of migration and scattering on the formation planetary proto-atmospheres and subsequent solid accretion onto planetary embryos. Title: Thermodynamic Analysis of Water-Rock Reactions in the Parent Body of Ryugu Authors: Shibuya, T.; Sekine, Y.; Kikuchi, S.; Kurokawa, H.; Fukushi, K.; Nakamura, T.; Watanabe, S. Bibcode: 2019LPICo2189.2095S Altcode: Thermodynamic modeling of water-chondrite reactions under various conditions suggests that a large redox gradient in the parent body could generate various secondary mineral assemblages and organic contents. Title: Modeling of Infrared Reflectance Spectra of Volatile-Rich Asteroids Authors: Kurokawa, H.; Shibuya, T.; Sekine, Y.; Ehlmann, B. L. Bibcode: 2019LPICo2189.2083K Altcode: We computed the model infrared reflectance spectra of asteroids using the results of chemical equilibrium calculations for water-rock reactions. We constrained the aqueous environments experienced by Ryugu, Bennu, Ceres, and the main-belt asteroids. Title: Laboratory Study on Morphological Features of Repeated Brine Flows on Mars: Implications for Detection of Hydrated Salts on Recurring Slope Lineae Authors: Imamura, S.; Sekine, Y.; Kurokawa, H.; Maekawa, Y.; Sasaki, T. Bibcode: 2019LPICo2089.6408I Altcode: Under martian small gravity, brine flow could form elongated streaks on Mars due to precipitated salts. Even if the precipitated salts exist on RSL, They are unlikely to be detected with CRISM because of the insufficient spatial resolution of CRISM. Title: A Forward Modeling of Infrared Reflectance Spectra of Asteroids: The Implications for Ryugu's Parent Body Authors: Kurokawa, H.; Shibuya, T.; Sekine, Y.; Ehlmann, B. L. Bibcode: 2019LPI....50.1815K Altcode: We show the model reflectance spectra of mineral assemblages obtained by chemical equilibrium calculations. We discuss the implications for Ryugu's parent body. Title: A Bayesian Approach to Deriving Ceres Surface Composition from Dawn VIR Data: Initial Quantification of Bright Spot and Typical Dark Material Phases with this Method Authors: Kurokawa, H.; Ehlmann, B. L.; Ammannito, E.; De Sanctis, M. C.; Lapotre, M.; Usui, T.; Stein, N. T.; Prettyman, T.; Raponi, A.; Ciarniello, M. Bibcode: 2018LPI....49.1908K Altcode: We determined Ceres surface composition and statistically rigorous error bars from Dawn VIR data using a Bayesian approach. Title: Hydrogen Isotopic Constraints on the Evolution of Surface and Subsurface Water on Mars Authors: Usui, T.; Kurokawa, H.; Wang, J.; Alexander, C. M. O'D.; Simon, J. I.; Jones, J. H. Bibcode: 2017LPI....48.1278U Altcode: We constrain the atmospheric loss and possible exchange of surface and subsurface water since 4 Ga based on our new D/H data of Noachian carbonates. Title: Tracing the Origin and Evolution of Volatiles on Mars: Constraints from Elemental and Isotopic Compositions of Nitrogen and Noble Gases Authors: Kurokawa, H.; Kurosawa, K.; Usui, T. Bibcode: 2017LPI....48.1204K Altcode: Using a model of the loss and supply of volatiles, we simulated the evolution of the atmospheric composition to constrain the origin of the volatiles on Mars. Title: The Evolution of Water in Martian Atmosphere, Hydrosphere, and Cryosphere: Insights from Hydrogen Isotopes Authors: Usui, T.; Kurokawa, H.; Alexander, C.; Simon, J. I.; Wang, J.; Jones, J. H. Bibcode: 2016AGUFM.P52A..04U Altcode: Mars exploration missions provide compelling evidence for the presence of liquid water during the earliest geologic era (Noachian: > 3.9 Ga) of Mars. The amount and stability of liquid water on the surface is strongly influenced by the composition and pressure of the atmosphere. However, the evolution of Noachian atmosphere has been poorly constrained due to uncertainties of atmospheric loss regimes and internal/external factors such as impact flux and volcanic degassing. We can trace the evolution of the early Martian atmosphere and its interaction with the hydrosphere and cryosphere with hydrogen isotope ratios (D/H) because they fractionate during atmospheric escape and during hydrological cycling between the atmosphere, surface waters, and the polar ice caps. This study reports D/H ratios of primordial and 4 Ga-old atmosphere by ion microprobe analyses of Martian meteorites. Analyses of olivine-hosted glass inclusions in the most primitive shergottite (Yamato 980459) provide a near-chondritic D/H ratio (1.3×SMOW) for the 4.5 Ga primordial water preserved in the mantle. On the other hand, carbonates in Allan Hills 84001 provide a D/H range (1.5-2.0×SMOW) for the Noachian surface water that was isotopically equilibrated with the 4 Ga atmosphere. The latter observation requires that even after the Noachian period the hydrogen isotopes were fractionated significantly to reach the present-day value of 6×SMOW. Using the one-reservoir model of Kurokawa et al. (2014) we can provide minimum estimates on the amounts of hydrogen loss before and after 4 Ga based on the D/H data from the meteorites (1.3×SMOW at 4.5 Ga and 1.5-2.0×SMOW at 4 Ga) assuming the volume of polar surface-ice (20-30 m global equivalent layers, GEL). The model indicates that the hydrogen loss during the first 0.5 billion years (16-54 m GEL) was comparable to those (42-93 mGEL) in the remaining Martian history. These values are distinctly lower than the geological estimates on the volumes of paleo-oceans (e.g., 550 mGEL, Di Achille & Hynek, 2010). This difference implies that a buried cryosphere must accounted for a large part of the water budget (Usui et al. 2015). Title: A Lower Limit of Atmospheric Pressure on Early Mars Inferred from Nitrogen and Argon Isotopes Authors: Kurokawa, H.; Kurosawa, K.; Usui, T. Bibcode: 2016LPI....47.1220K Altcode: Comparing model calculations of the atmospheric evolution with isotope data of trapped gas in ALH 84001 gave a lower limit of the atmospheric pressure at 4.1 Ga. Title: Escape of Early Martian Atmosphere and Hydrosphere: Constraints from Isotopic Compositions Authors: Kurokawa, H.; Kurosawa, K.; Usui, T. Bibcode: 2015LPI....46.1643K Altcode: 2015LPICo1832.1643K This study of the evolution of the martian isotopic compositions suggests the presence of thick early atmosphere lost during the heavy bombardment period. Title: The Effect of Compositional Inhomogeneity on Radii of Hot Jupiters Authors: Kurokawa, H.; Inutsuka, S. Bibcode: 2015LPI....46.1710K Altcode: 2015LPICo1832.1710K We evaluate the effect of compositional inhomogeneity on radii of hot Jupiters by a structure calculation with self-consistent treatment of convection regimes. Title: Hydrogen Isotopes Record the History of the Martian Hydrosphere and Atmosphere Authors: Usui, T.; Simon, J. I.; Jones, J. H.; Kurokawa, H.; Sato, M.; Alexander, C. M. O'D.; Wang, J. Bibcode: 2015LPI....46.1593U Altcode: 2015LPICo1832.1593U This study presents insights from hydrogen isotopes for the origin and evolution of martian water reservoirs. Title: Evolution of water reservoirs on Mars: Constraints from hydrogen isotopes in martian meteorites Authors: Kurokawa, H.; Sato, M.; Ushioda, M.; Matsuyama, T.; Moriwaki, R.; Dohm, J. M.; Usui, T. Bibcode: 2014E&PSL.394..179K Altcode: 2014arXiv1403.4211K Martian surface morphology implies that Mars was once warm enough to maintain persistent liquid water on its surface. While the high D/H ratios (∼6 times the Earth's ocean water) of the current martian atmosphere suggest that significant water has been lost from the surface during martian history, the timing, processes, and the amount of the water loss have been poorly constrained. Recent technical developments of ion-microprobe analysis of martian meteorites have provided accurate estimation of hydrogen isotope compositions (D/H) of martian water reservoirs at the time when the meteorites formed. Based on the D/H data from the meteorites, this study demonstrates that the water loss during the pre-Noachian (>41-99 m global equivalent layers, GEL) was more significant than in the rest of martian history (>10-53 m GEL). Combining our results with geological and geomorphological evidence for ancient oceans, we propose that undetected subsurface water/ice (≃100-1000 m GEL) should exist, and it exceeds the observable present water inventory (≃20-30 m GEL) on Mars. Title: Mass-loss Evolution of Close-in Exoplanets: Evaporation of Hot Jupiters and the Effect on Population Authors: Kurokawa, H.; Nakamoto, T. Bibcode: 2014ApJ...783...54K Altcode: 2014arXiv1401.2511K During their evolution, short-period exoplanets may lose envelope mass through atmospheric escape owing to intense X-ray and extreme ultraviolet (XUV) radiation from their host stars. Roche-lobe overflow induced by orbital evolution or intense atmospheric escape can also contribute to mass loss. To study the effects of mass loss on inner planet populations, we calculate the evolution of hot Jupiters considering mass loss of their envelopes and thermal contraction. Mass loss is assumed to occur through XUV-driven atmospheric escape and the following Roche-lobe overflow. The runaway effect of mass loss results in a dichotomy of populations: hot Jupiters that retain their envelopes and super Earths whose envelopes are completely lost. Evolution primarily depends on the core masses of planets and only slightly on migration history. In hot Jupiters with small cores (sime 10 Earth masses), runaway atmospheric escape followed by Roche-lobe overflow may create sub-Jupiter deserts, as observed in both mass and radius distributions of planetary populations. Comparing our results with formation scenarios and observed exoplanets populations, we propose that populations of closely orbiting exoplanets are formed by capturing planets at/inside the inner edges of protoplanetary disks and subsequent evaporation of sub-Jupiters. Title: Mass-Loss Evolution of Super-Earths: Effects of Stellar Types Authors: Kurokawa, H.; Kaltenegger, L.; Nakamoto, T. Bibcode: 2014LPI....45.1355K Altcode: We show evolution of super-Earths with H/He envelopes, considering XUV-driven escape and Roche-lobe overflow. Their compositions are shaped by mass loss. Title: Thickness of Martian Ground Ice: Implication from Multi-Water-Reservoir Model Authors: Kurokawa, H.; Usui, T.; Demura, H.; Sato, M. Bibcode: 2014LPI....45.1815K Altcode: Recent observations propose the existence of ground ice on Mars. Our model suggests that the thickness is at least a few hundred meters based on D/H data. Title: Atmospheric mass-loss and evolution of short-period exoplanets: the examples of CoRoT-7b and Kepler-10b Authors: Kurokawa, H.; Kaltenegger, L. Bibcode: 2013MNRAS.433.3239K Altcode: 2013arXiv1306.0973K; 2013MNRAS.tmp.1613K Short-period exoplanets potentially lose envelope masses during their evolution because of atmospheric escape caused by the intense X-ray and extreme UV (XUV) radiation from their host stars. We develop a combined model of atmospheric mass-loss calculation and thermal evolution calculation of a planet to simulate its evolution and explore the dependences on the formation history of the planet. Thermal atmospheric escape as well as the Roche lobe overflow contributes to mass-loss. The maximum initial planetary model mass depends primarily on the assumed evolution model of the stellar XUV luminosity. We adapt the model to CoRoT-7b and Kepler-10b to explore the evolution of both planets and the maximum initial mass of these planets. We take the recent X-ray observation of CoRoT-7 into account and explore the effect of different XUV evolution models on the planetary initial mass. Our calculations indicate that both hot super-Earths could be remnants of Jupiter-mass gas planets. Title: Significant Water Loss During Noachian Era: Constraints from Hydrogen Isotopes in Martian Meteorites Authors: Kurokawa, H.; Sato, M.; Ushioda, M.; Matsuyama, T.; Moriwaki, R.; Usui, T. Bibcode: 2013LPI....44.1853K Altcode: 2013LPICo1719.1853K Based on the D/H data from the meteorites, we determine the amount of water loss during Noachian and post-Noachian periods. Title: A Study on Red Asymmetry of Hα Flare Ribbons Using a Narrowband Filtergram in the 2001 April 10 Solar Flare Authors: Asai, Ayumi; Ichimoto, Kiyoshi; Kita, Reizaburo; Kurokawa, Hiroki; Shibata, Kazunari Bibcode: 2012PASJ...64...20A Altcode: 2011arXiv1112.5912A We report on a detailed examination of the ``red asymmetry'' of the Hα emission line seen during the 2001 April 10 solar flare by using a narrowband filtergram. We investigated the temporal evolution and the spatial distribution of the red asymmetry by using Hα data taken with the 60-cm Domeless Solar Telescope at Hida Observatory, Kyoto University. We confirmed that the red asymmetry clearly appeared all over the flare ribbons, and the strong red asymmetry is located on the outer narrow edges of the flare ribbons, with a width of about 1.5"-3.0" (1000-2000 km), where strong energy releases occur. Moreover, we found that the red asymmetry, which also gives a measure of the Doppler shift of the Hα emission line, concentrates on a certain value, not depending on the intensity of the Hα kernels. This implies not only that the temporal evolutions of the red asymmetry and those of the intensity are not synchronous in each flare kernel, but also that the peak asymmetry (or velocity of the chromospheric condensation) of individual kernel is not a strong function of their peak intensity. Title: Radiation Limits of Ocean Planets: Effects of the Atmospheric Absorption of the Incoming Radiation with One-Dimensional Radiative-Convective Equilibrium Model Authors: Kurokawa, H.; Nakamoto, T. Bibcode: 2011LPI....42.1328K Altcode: We investigate the effects of the absorption of the incoming radiation on the radiation limit of the troposphere of ocean planets. To clarify the effects, we use a simple parameterization of the absorption. We have found two important cases. Title: Energetic Relations between the Disappearing Solar Filaments and the Associated Flare Arcades Authors: Morimoto, Taro; Kurokawa, Hiroki; Shibata, Kazunari; Ishii, Takako T. Bibcode: 2010PASJ...62..939M Altcode: We present the temporal and statistical relations between the mechanical energies of disappearing solar filaments and the thermal energies of the associated flare arcades in soft X-rays. Measuring the 3-D velocity fields of 10 eruptive filaments, we calculated their mechanical energy gain rate, ɛmc, per unit volume and compared it to the thermal energy release rate per unit volume, ɛth, derived with Yohkoh/SXT data. For the statistical relation, we found a relation that can be approximated as ɛth ∝ ɛ1.9mc. This relation can be explained by interpreting the energy input to an arcade via the Poynting flux in the magnetic reconnection process and the acceleration of a filament by the Lorentz force. This explanation is also supported by the strong dependence of the observed increase rates of both the thermal and mechanical energy densities on the mean magnetic field strength of the source region. We also investigated their temporal variations, and found that the start time of increase in the mechanical energy of a filament preceded that of the thermal energy of the coronal arcade in some cases. These relations imply that the basic mechanisms that accelerate a filament and create a hot plasma are different, and both energy increase rates are determined primary by the magnetic field strengths. Title: New Observation of Failed Filament Eruptions: The Influence of Asymmetric Coronal Background Fields on Solar Eruptions Authors: Liu, Y.; Su, J.; Xu, Z.; Lin, H.; Shibata, K.; Kurokawa, H. Bibcode: 2009ApJ...696L..70L Altcode: Failed filament eruptions not associated with a coronal mass ejection (CME) have been observed and reported as evidence for solar coronal field confinement on erupting flux ropes. In those events, each filament eventually returns to its origin on the solar surface. In this Letter, a new observation of two failed filament eruptions is reported which indicates that the mass of a confined filament can be ejected to places far from the original filament channel. The jetlike mass motions in the two failed filament eruptions are thought to be due to the asymmetry of the background coronal magnetic fields with respect to the locations of the filament channels. The asymmetry of the coronal fields is confirmed by an extrapolation based on a potential field model. The obvious imbalance between the positive and negative magnetic flux (with a ratio of 1:3) in the bipolar active region is thought to be the direct cause of the formation of the asymmetric coronal fields. We think that the asymmetry of the background fields can not only influence the trajectories of ejecta, but also provide a relatively stronger confinement for flux rope eruptions than the symmetric background fields do. Title: The Power-Law Distribution of Flare Kernels and Fractal Current Sheets in a Solar Flare Authors: Nishizuka, N.; Asai, A.; Takasaki, H.; Kurokawa, H.; Shibata, K. Bibcode: 2009ApJ...694L..74N Altcode: 2013arXiv1301.6244N We report a detailed examination of the fine structure inside flare ribbons and the temporal evolution of this fine structure during the X2.5 solar flare that occurred on 2004 November 10. We examine elementary bursts of the C IV (~1550 Å) emission lines seen as local transient brightenings inside the flare ribbons in the ultraviolet (1600 Å) images taken with Transition Region and Coronal Explorer, and we call them C IV kernels. This flare was also observed in Hα with the Sartorius 18 cm Refractor telescope at Kwasan observatory, Kyoto University, and in hard X-rays (HXR) with Reuven Ramaty High Energy Solar Spectroscopic Imager. Many C IV kernels, whose sizes were comparable to or less than 2'', were found to brighten successively during the evolution of the flare ribbon. The majority of them were well correlated with the Hα kernels in both space and time, while some of them were associated with the HXR emission. These kernels were thought to be caused by the precipitation of nonthermal particles at the footpoints of the reconnecting flare loops. The time profiles of the C IV kernels showed intermittent bursts, whose peak intensity, duration, and time interval were well described by power-law distribution functions. This result is interpreted as evidence for "self-organized criticality" in avalanching behavior in a single flare event, or for fractal current sheets in the impulsive reconnection region. Title: Multi-scale reconnections in a complex CME Authors: van Driel-Gesztelyi, L.; Goff, C. P.; Démoulin, P.; Culhane, J. L.; Matthews, S. A.; Harra, L. K.; Mandrini, C. H.; Klein, K. -L.; Kurokawa, H. Bibcode: 2008AdSpR..42..858V Altcode: A series of three flares of GOES class M, M and C, and a CME were observed on 20 January 2004 occurring in close succession in NOAA 10540. Types II, III, and N radio bursts were associated. We use the combined observations from TRACE, EIT, Hα images from Kwasan Observatory, MDI magnetograms, GOES, and radio observations from Culgoora and Wind/ WAVES to understand the complex development of this event. We reach three main conclusions. First, we link the first two impulsive flares to tether-cutting reconnections and the launch of the CME. This complex observation shows that impulsive quadrupolar flares can be eruptive. Second, we relate the last of the flares, an LDE, to the relaxation phase following forced reconnections between the erupting flux rope and neighbouring magnetic field lines, when reconnection reverses and restores some of the pre-eruption magnetic connectivities. Finally, we show that reconnection with the magnetic structure of a previous CME launched about 8 h earlier injects electrons into open field lines having a local dip and apex (located at about six solar radii height). This is observed as an N-burst at decametre radio wavelengths. The dipped shape of these field lines is due to large-scale magnetic reconnection between expanding magnetic loops and open field lines of a neighbouring streamer. This particular situation explains why this is the first N-burst ever observed at long radio wavelengths. Title: Three Successive and Interacting Shock Waves Generated by a Solar Flare Authors: Narukage, Noriyuki; Ishii, Takako T.; Nagata, Shin'ichi; UeNo, Satoru; Kitai, Reizaburo; Kurokawa, Hiroki; Akioka, Maki; Shibata, Kazunari Bibcode: 2008ApJ...684L..45N Altcode: We discovered three successive Moreton waves generated by a single solar flare on 2005 August 3. Although this flare was not special in magnitude or configuration, Moreton waves (shock waves) successively occurred three times. Multiple shock waves generated during a single flare have not been reported before. Furthermore, the faster second-generated Moreton wave caught up and merged with the slower first-generated one. This is the first report of shock-shock interaction associated with a solar flare. The shock-plasma interaction was also detected. When the third-generated Moreton wave passed through an erupting filament, the filament was accelerated by the Moreton wave. In this event, filaments also erupted three times. On the basis of this observation, we consider that filament eruption is indispensable to the generation of Moreton waves. Title: Observation of Magnetic Field Reconnection at the Base of EFR Surges Authors: Kurokawa, H.; Liu, Y.; Sano, S.; Ishii, T. T. Bibcode: 2007ASPC..369..347K Altcode: We show that surges are the first manifestation of the birth of emerging flux region (EFR) or active regions by demonstarating the evolutions of the earliest stage of EFRs. We call such surges as EFR-surges. We show that almost all surges are associated with the increase or new emergence of the satellite polarity flux at their bases, by presenting the results of quantitative analyses of the magnetic field variations in the surge bases. Our finding is that the eleven of fourteen events showed the increase of the magnetic flux of isolated or satellite polarity at the bases of the surges. Examining these results, we conclude that the emergence of new magnetic flux plays an essential role for the production of Hα surges and that the magnetic fileld reconnection between the EFR and the pre-existing and surounding magnetic field produces surges. We also discuss the future observational target to confirm the validity of the magnetic reconnection model of surges in more details by using the SOT of Solar-B. Title: The Relationship between EUV Brightenings and Dark Mottles in the Quiet Sun Authors: Kamio, S.; Kurokawa, H.; Brooks, D. H. Bibcode: 2007ASPC..369..257K Altcode: The relationship between EUV brightenings in the transition region and dark mottles in the chromosphere is studied using data obtained in an observational campaign between the Coronal Diagnostic Spectrometer (CDS) on SOHO and the Domeless Solar Telescope (DST) at Hida Observatory. We found several examples of EUV brightenings accompanied by upflowing dark mottles in the chromosphere. This suggests that EUV blinkers are formed by the heating of dark mottles or spicules. Title: Observation of Interactions and Eruptions of Two Filaments Authors: Su, Jiangtao; Liu, Yu; Kurokawa, Hiroki; Mao, Xinjie; Yang, Shangbin; Zhang, Hongqi; Wang, Haimin Bibcode: 2007SoPh..242...53S Altcode: We present new observations of the interactions of two close, but distinct, Hα filaments and their successive eruptions on 5 November 1998. The magnetic fields of the filaments are both of the sinistral type. The interactions between the two filaments were initiated mainly by an active filament of one of them. Before the filament eruptions, two dark plasma ejections and chromospheric brightenings were observed. They indicate that possible magnetic reconnection had occurred between the two filaments. During the first filament eruption, salient dark mass motions transferring from the left erupting filament into the right one were observed. The right filament erupted 40 minutes later. This second filament eruption may have been the result of a loss of stability owing to the sudden mass injection from the left filament. Based on the Hα observations, we have created a sketch for understanding the interactions between two filaments and accompanying activities. The traditional theory of filament merger requires that the filaments share the same filament channel and that the reconnection occurs between the two heads, as simulated by DeVore, Antiochos, and Aulanier (Astrophys. J.629, 1122, 2005; 646, 1349, 2006). Our interpretation is that the external bodily magnetic reconnection between flux ropes of the same chirality is another possible way for two filament bodies to coalesce. Title: Evolution of Magnetic Nonpotentiality in NOAA AR 10486 Authors: Dun, J.; Kurokawa, H.; Ishii, T. T.; Liu, Y.; Zhang, H. Bibcode: 2007ApJ...657..577D Altcode: The active region NOAA 10486 was one of the most flare-productive regions during solar cycle 23. In this paper, we focus our analysis on the daily evolution of magnetic nonpotentiality for this region from 2003 October 26 to October 30. Daily averaged values of three nonpotential parameters: magnetic shear angle, line-of-sight current, and current helicity of the selected regions along the main neutral lines are calculated using the vector magnetograms obtained at Huairou Solar Observing Station. The magnetic flux evolution and proper motion of magnetic features are also studied in detail for the initial brightening regions of the two large X-class flares (X17 on October 28 and X10 on October 29). The main results are as follows. (1) Three parameters of the magnetic nonpotentiality in the photosphere obviously increased at the impulsively brightening flare sites from at least 1 day before the two large X-class flares, and most of the three parameters decreased after the flares around the main flare regions. (2) The increase of magnetic flux and complex proper motions of the magnetic knots were found to be simultaneously occurring at the non-potentiality developing sites along the main neutral lines. Such increases and motions of the magnetic flux can be explained by the model of emerging twisted flux ropes, and we conclude that the emergence of twisted magnetic flux ropes are a main reason for the development of nonpotentiality along the neutral line and for the production of strong X-class flares. Title: A Multiple Flare Scenario where the Classic Long-Duration Flare Was Not the Source of a CME Authors: Goff, C. P.; van Driel-Gesztelyi, L.; Démoulin, P.; Culhane, J. L.; Matthews, S. A.; Harra, L. K.; Mandrini, C. H.; Klein, K. L.; Kurokawa, H. Bibcode: 2007SoPh..240..283G Altcode: A series of flares (GOES class M, M and C) and a CME were observed in close succession on 20 January 2004 in NOAA 10540. Radio observations, which took the form of types II, III and N bursts, were associated with these events. We use the combined observations from TRACE, EIT, Hα images from Kwasan, MDI magnetograms and GOES to understand the complex development of this event. Contrary to a standard interpretation, we conclude that the first two impulsive flares are part of the CME launch process while the following long-duration event flare represents simply the recovery phase. Observations show that the flare ribbons not only separate but also shift along the magnetic inversion line so that magnetic reconnection progresses stepwise to neighboring flux tubes. We conclude that "tether cutting" reconnection in the sheared arcade progressively transforms it to a twisted flux tube, which becomes unstable, leading to a CME. We interpret the third flare, a long-duration event, as a combination of the classical two-ribbon flare with the relaxation process following forced reconnection between the expanding CME structure and neighboring magnetic fields. Title: The X10 Flare on 29 October 2003: Was It Triggered by Magnetic Reconnection between Counter-Helical Fluxes? Authors: Liu, Yu; Kurokawa, Hiroki; Liu, Chang; Brooks, David H.; Dun, Jingping; Ishii, Takako T.; Zhang, Hongqi Bibcode: 2007SoPh..240..253L Altcode: 2007astro.ph..1794L Vector magnetograms taken at Huairou Solar Observing Station (HSOS) and Mees Solar Observatory (MSO) reveal that the super active region (AR) NOAA 10486 was a complex region containing current helicity flux of opposite signs. The main positive sunspots were dominated by negative helicity fields, while positive helicity patches persisted both inside and around the main positive sunspots. Based on a comparison of two days of deduced current helicity density, pronounced changes associated with the occurrence of an X10 flare that peaked at 20:49 UT on 29 October 2003 were noticed. The average current helicity density (negative) of the main sunspots decreased significantly by about 50%. Accordingly, the helicity densities of counter-helical patches (positive) were also found to decay by the same proportion or more. In addition, two hard X-ray (HXR) "footpoints" were observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) during the flare in the 50 - 100 keV energy range. The cores of these two HXR footpoints were adjacent to the positions of two patches with positive current helicity that disappeared after the flare. This strongly suggested that the X10 flare on 29 October 2003 resulted from reconnection between magnetic flux tubes having opposite current helicity. Finally, the global decrease of current helicity in AR 10486 by ∼50% can be understood as the helicity launched away by the halo coronal mass ejection (CME) associated with the X10 flare. Title: An Hα Surge Provoked by Moving Magnetic Features near an Emerging Flux Region Authors: Brooks, D. H.; Kurokawa, H.; Berger, T. E. Bibcode: 2007ApJ...656.1197B Altcode: We present a detailed study of Hα surges from cotemporal high-resolution multiwavelength images of NOAA AR 8227 obtained by the 50 cm Swedish Vacuum Solar Telescope (formerly situated on La Palma, Spain) and TRACE. We find that two kinds of collisions between opposite polarity magnetic flux produce the surges. First, one edge of an emerging flux region (EFR) collides with the preexisting magnetic field and causes continual surge activities, which have already been named EFR surges by previous authors. Secondly, moving magnetic features (MMFs), which emerge near the sunspot penumbra, pass through the ambient plasma and eventually collide with the opposite polarity magnetic field of the EFR. During their passage from the sunspot penumbra to the EFR, the MMFs constantly interacted with other magnetic elements and had a close relationship and showed similar flow patterns to Ca II K bright points. These brightenings were located at the leading edges of the MMFs. Cancellation of opposite polarity magnetic flux at the surge footpoint is observed, accompanied by chromospheric and coronal brightenings. We explain the evolutionary and morphological characteristics of the multiwavelength features associated with the Hα surges in both cases by the extension of previous 2D schematic models of reconnection in surges. Furthermore, by measuring the expansion velocity and photospheric magnetic field around the surge footpoint, we estimate a dimensionless reconnection rate of 0.04 (ratio of inflow velocity to Alfvén velocity). This is sufficient to produce a significant surge that heats the chromospheric plasma to coronal temperatures. Title: Build-up of a CME and its Interaction with Large-Scale Magnetic Structures Authors: van Driel-Gesztelyi, L.; Goff, C. P.; Demoulin, P.; Culhane, J. L.; Klein, K. L.; Mandrini, C. H.; Matthews, S. A.; Harra, K. L.; Kurokawa, H. Bibcode: 2006IAUJD...3E..86V Altcode: Introduction: A series of flares (GOES class M, M and C) and a CME were observed on 20-JAN-2004 occurring in close succession in NOAA 10540. Types II, III and a N radio bursts were associated. We investigate the link between the flares (two impulsive flares followed by an LDE) and the CME as well as the origin of the rare decametric N-burst. Methods: We use the combined observations from TRACE, SOHO/EIT, H-alpha images from Kwasan Observatory, SOHO/MDI magnetograms, GOES and radio observations from Culgoora and Wind/WAVES as well as magnetic modelling to understand the complex development of this event. Results: We link the first two impulsive flares to tether-cutting reconnections and the launch of the CME, while the last of the flares, an LDE, to the relaxation phase following forced reconnections between the erupting flux rope and neighbouring magnetic field lines. We show that reconnection with the magnetic structure of a previous CME, launched about 8 hours earlier, injects electrons into open field lines having a local dip and apex of about 6 solar radii height. The dipped shape of these field lines was due to large-scale magnetic reconnection between expanding magnetic loops and open field lines of a neighbouring streamer. This particular situation explains the observed decametric N burst. Discussion: This complex observation shows that impulsive quadrupolar flares can be eruptive, while an LDE may remain a confined event. We find that reconnection forced by the expanding CME structure is followed by a relaxation phase, when reconnection reverses and restores some of the pre-eruption magnetic connectivities. The observed decametric N-burst was caused by the interaction of two CMEs and reconnection of their expanding magnetic field with neighbouring streamer field lines - a very particular interplay, which explains why N-bursts are so rare. Title: Magnetic Field Configuration and Evolution of a Highly Flare-producitve Region NOAA 10808 (2005-Sep) Authors: Ishii, T. T.; Nagashima, K.; Kurokawa, H.; Kitai, R.; Ueno, S.; Nagata, S.; Shibata, K. Bibcode: 2006IAUJD...3E..59I Altcode: Active regions on the Sun have different flare productivities with each other. Some regions produce many large flares, while others produce no flares. The key factor of a high flare productivity is the complexity of magnetic field configuration of the region. In our previous studies, we found that the twisted structure of emerging magnetic flux bundles is the essential feature of flare-productive active regions. Vector magnetic field data sets are necessary to examine the twisted magnetic field structures (e.g., shear and helicity). Recently we have constructed our new telescope, Solar Magnetic Activity Research Telescope (SMART) at Hida Observatory, Kyoto University. We can obtain high resolution full disk H-alpha images (with Lyot filter; H-alpha center, blue and reg wing) and full disk vector magnetograms with SMART. The active region NOAA 10808 showed the highest flare activity during the current solar cycle (cycle 23) in September 2005. We studied the formation process of delta-type magnetic configuration using SOHO/MDI magnetograms and flares using TRACE data. We also studied the evolution of magnetic shear and H-alpha filaments using H-alpha full disk images and full disk vector magnetograms obtained with SMART. In this paper, we summarize the characteristics of magnetic field configuration of this region and discuss the relation between the configuration and the high flare activity. Title: The relation between Ca bright grains and oscillations in the photosphere Authors: Kamio, S.; Kurokawa, H. Bibcode: 2006A&A...450..351K Altcode: Context: .Ca bright grains are small and repetitive brightenings ubiquitously found in the quiet Sun.
Aims: .The relationship between the formation of Ca bright grains and the dynamics in the chromosphere and the photosphere is studied.
Methods: .We simultaneously observed the time series of spectra in Ca II H, Hα, and Fe I with the horizontal spectrograph of the Domeless Solar Telescope (DST) at Hida Observatory.
Results: .Our wavelet analysis revealed that the occurrence of Ca II H 2V brightenings are correlated with enhanced 5 mHz velocity oscillations in the chromosphere and the photosphere.
Conclusions: .Ca bright grains can be explained by acoustic shocks in the chromosphere that are associated with 5 mHz oscillations in the photosphere below. Title: Horizontal and Vertical Flow Structure in Emerging Flux Regions Authors: Kozu, Hiromichi; Kitai, Reizaburo; Brooks, David H.; Kurokawa, Hiroki; Yoshimura, Keiji; Berger, Thomas E. Bibcode: 2006PASJ...58..407K Altcode: In order to obtain an overall view of the flow structure of convective gas in emerging flux regions (EFRs), we studied three EFRs in two solar active regions, NOAA 8218 and NOAA 10774. Using the Local Correlation Tracking method, we found several horizontally divergent flow structures, which were stable over a period of 1 hour, in 2 EFRs in NOAA 8218. The horizontal flow velocities and the sizes of the structures were around 500m s-1 and about 4Mm in radius, respectively. We analyzed another dataset of NOAA 10774 using spectroscopic methods and found temporarily stable up-ward gas flows in the central part of the EFR. The line-of-sight velocities were around 150m s-1 and the size of the flow patch was 2 to 5Mm in radius. These results support our previous findings that convective-cell-like flow appears in the central part of an EFR. We estimated from these results that the depth of the flow cell in EFRs is about 600km, and the turn-over time of the cell is about 2 hours. Title: Multi-scale reconnections in a complex CME Authors: van Driel-Gesztelyi, L.; Goff, C.; Demoulin, P.; Culhane, J. L.; Matthews, S. A.; Harra, L. K.; Mandrini, C. H.; Klein, K. L.; Kurokawa, H. Bibcode: 2006cosp...36.2371V Altcode: 2006cosp.meet.2371V A series of flares GOES class M M and C and a CME were observed on 20-JAN-2004 occurring in close succession in NOAA 10540 Types II III and an N radio bursts were associated We use the combined observations from TRACE EIT H-alpha images from Kwasan Observatory MDI magnetograms GOES and radio observations from Culgoora and Wind WAVES to understand the complex development of this event We link the first two impulsive flares to tether-cutting reconnections and the launch of the CME while the last of the flares an LDE to the relaxation phase following forced reconnections between the erupting flux rope and neighbouring magnetic field lines We show that reconnection with the magnetic structure of a previous CME launched about 8 hours earlier injects electrons into open field lines having a local dip and apex of about 6 solar radii height The dipped shape of these field lines was due to large-scale magnetic reconnection between expanding magnetic loops and open field lines of a neighbouring streamer This particular situation explains the observed decametric N burst and why N-bursts are so rare Title: Close causal relation between emergence of twisted flux rope and strong flares Authors: Kurokawa, H.; Ishii, T.; Ueno, S.; Nagata, S.; Kitai, R. .; Shibata, K. Bibcode: 2006cosp...36.2230K Altcode: 2006cosp.meet.2230K Solar flares are considered to occur in the solar corona by magnetic field reconnection Shibata 1995 The flare energy which is stored in the twisted magnetic field is supplied to the corona through the photosphere from the convection zone For this reason observations of evolutional changes in the magnetic field configuration of flare-productive regions are fundamentally important for the flare energy build-up study and the forecast of strong flares Hagyard 1984 showed that flares occurred along the neutral line of strong magnetic shear The magnetic shear is however not a sufficient condition for strong flare occurrence and it is important to study the active region evolutions and examine which type of magnetic shear development produces strong flares Until now several works made detailed studies of magnetic shear developments in flare-productive sunspot regions and suggested that the emergence of a twisted magnetic flux rope which is originally formed in the convection zone must be the source of the strong magnetic shear development in a sunspot region to produce a strong flare activity Kurokawa 1987 Tanaka 1991 Ishii et al 1998 Kurokawa 2002 In this paper we present our recent studies of energy build-up processes of flare-productive active regions We studied the evolutional changes of 11 super active regions which produced more than three X-class flares observed from 1998 through 2005 during the 23 solar sunspot cycle in details We found all these regions show some common magnetic evolutional features in the course of the Title: CAWSES Related Projects in Japan : Grant-in-Aid for Creative Scientific Research ügBasic Study of Space Weather Predictionüh and CHAIN (Continuous H Alpha Imaging Network) Authors: Shibata, K.; Kurokawa, H. Bibcode: 2006cosp...36.3288S Altcode: 2006cosp.meet.3288S The Grant-in-Aid for Creative Scientific Research of the Ministry of Education Science Sports Technology and Culture of Japan The Basic Study of Space Weather Prediction PI K Shibata Kyoto Univ has started in 2005 as 5 years projects with total budget 446Myen The purpose of this project is to develop a physical model of solar-terrestrial phenomena and space storms as a basis of space weather prediction by resolving fundamental physics of key phenomena from solar flares and coronal mass ejections to magnetospheric storms under international cooperation program CAWSES Climate and Weather of the Sun-Earth System Continuous H Alpha Imaging Network CHAIN Project led by H Kurokawa is a key project in this space weather study enabling continuous H alpha full Sun observations by connecting many solar telescopes in many countries through internet which provides the basis of the study of space weather prediction Title: a Series of Compact Flares with AN Associated CME Authors: Goff, C. P.; van Driel-Geszrelyi, L.; Culhane, J. L.; Matthews, S. A.; Harra, L. K.; Démoulin, P.; Mandrini, C. H.; Kurokawa, H. Bibcode: 2005ESASP.600E.157G Altcode: 2005ESPM...11..157G; 2005dysu.confE.157G No abstract at ADS Title: Multi-Line Spectroscopy of Grains Authors: Kamio, S.; Kurokawa, H. Bibcode: 2005ESASP.600E..18K Altcode: 2005ESPM...11...18K; 2005dysu.confE..18K No abstract at ADS Title: Evolution of Barb Angle and Filament Eruption Authors: Su, J. T.; Liu, Y.; Zhang, H. Q.; Kurokawa, H.; Yurchyshyn, V.; Shibata, K.; Bao, X. M.; Wang, G. P.; Li, C. Bibcode: 2005ApJ...630L.101S Altcode: Hα observations of a quiescent U-shaped filament were obtained at Big Bear Solar Observatory and at Hida Observatory with the Flare Monitoring Telescope. The filament was located in the southern hemisphere on 1998 November 4. We study the evolution of the angle of a barb with respect to the axis of the filament and find the evolution can be divided into two phases: a rise from the acute phase to the obtuse phase and a fall. Thus, this indicates that the chirality of this barb changes with time. Moreover, in the process of evolution, we find that interconnection of the part of the filament bearing the barb with the whole filament became either weakened or strengthened. We impute the final eruption of the filament to the chirality evolution of the barb. Title: Production of Filaments by Surges Authors: Liu, Yu; Kurokawa, Hiroki; Shibata, Kazunari Bibcode: 2005ApJ...631L..93L Altcode: We have recently developed a new method for automatic detection of solar surges and other dark dynamic features. For the first time we find that some filaments can be quickly formed by trapping the cold material supplied by surges originating from the chromosphere. Two clear examples are presented in this Letter, showing the special process for new filament formation by surge injection. The data used here were taken from Hida Observatory and the Global Hα Network operated by Big Bear Solar Observatory. Both the filaments existed on the solar surface for not less than 20 hr, with an average length about 200", and had obvious helical structures and barbs. The surge material was injected from one terminal along the main axis of the filaments or the filament channels. We conclude that there are two necessary conditions for new filament formation by surges at one location: (1) an ``empty'' filament channel, or magnetic trap, and (2) enough mass supplied by surge activity. In most other surge-filament events, apart from our two examples, the surges are observed moving toward and acting on a preexisting nearby filament. The close relationship between surge activity and filament formation and maintenance suggests that there should be a direct link between the filament axial fields and the large-scale background fields along which the surge material can be driven into the filament channel. On the other hand, it also supports the idea that the frequent injection of flow from below is an important way to convey mass and energy into the corona through magnetic reconnections driven by successive emerging flux and converging flow. Title: Observations of an Emerging Flux Region Surge: Implications for Coronal Mass Ejections Triggered by Emerging Flux Authors: Liu, Y.; Su, J. T.; Morimoto, T.; Kurokawa, H.; Shibata, K. Bibcode: 2005ApJ...628.1056L Altcode: It is well known that coronal mass ejections (CMEs) are often associated with flares and filament eruptions. Previous studies of CMEs, however, have not established any association between CMEs and surges. In this paper, we present a detailed analysis of a large emerging flux region (EFR) surge and a jetlike CME, both observed on 1998 April 16. Our analysis shows a close temporal and spatial relationship between the two. Using observations from the Large Angle and Spectrometric Coronagraph (LASCO) and Hida Flare Monitoring Telescope (Hα, Hα+/-0.8 Å), we found that the CME's onset time and central position angle were coincident with the surge features. Magnetograms and Hα filtergrams showed that the surge resulted from the successive emergence of a bipolar sunspot group, NOAA Active Region 8203, which was the only active region in the northern hemisphere. The surge was impulsively accelerated at around the peak time of the GOES SXR flux. The associated CME appeared in the field of view of LASCO C2 16 minutes after the surge disappeared. Importantly, observations from the EUV Imaging Telescope at λ195 Å clearly demonstrate topological changes in the coronal field due to its interaction with the EFR. An initially closed EFR-loop system opened up during the surge. There was no filament involved in this surge-CME event. We propose that the onset of the CME resulted from the significant restructuring of the large-scale coronal magnetic field as a result of flux emergence in the active region. This surge-CME event strongly suggests that emerging flux may not only trigger a surge but also simultaneously trigger a CME by means of small-scale reconnection in the lower atmosphere. Title: Transition Region Downflows in the Impulsive Phase of Solar Flares Authors: Kamio, S.; Kurokawa, H.; Brooks, D. H.; Kitai, R.; UeNo, S. Bibcode: 2005ApJ...625.1027K Altcode: We present observations of four flares that occurred during coordinated observations between the Coronal Diagnostic Spectrometer (CDS) on board SOHO and the Domeless Solar Telescope (DST) at Hida Observatory. We studied the evolution of relative Doppler velocities in the flare kernels by using He I (3.5×104 K), O V (2.2×105 K), and Mg IX (1.0×106 K) spectra obtained with high time cadence (42 s) SOHO CDS observations and the Hα monochromatic images obtained with the DST. We found that the transition region plasma of O V showed strong downward velocities up to 87 km s-1 simultaneously with the downflows in the lower temperature chromospheric emissions in He I and Hα during the impulsive phase of all four flares. From these results we suggest that the downflows in the transition region and the chromosphere are a common feature in the impulsive phase of flares. For the Mg IX line we did not detect any significant change in velocity, which suggests that the 106 K plasma was close to the intermediate temperature between the upflowing plasma (107 K) and the downflowing plasma (104-105 K). These are important for understanding the dynamics of the solar atmosphere in response to the sudden energy deposition of a flare. Title: A Study On Surges: I. Automatic Detection Of Dynamic Hα Dark Features From High-Cadence Full-Disk Observations Authors: Liu, Y.; Kurokawa, H.; Kitai, R.; Ueno, S.; Su, J. T. Bibcode: 2005SoPh..228..149L Altcode: We present a new method for the automatic identification and classification of dynamic Hα dark features found in time series of full-disk solar images at three Hα wavelengths (center, and ± 0.8 Å). The simultaneous Hα observations are obtained by the multi-channel Flare Monitoring Telescope (FMT) at Hida Observatory. The program was developed in order to replace the present visual detection and classification of the phenomena. Usually, an obvious dark feature found in the Hα −0.8 Å observations probably corresponds to some phenomenon such as a surge or chromospheric network enhancement, or filament activity. Thus, one of our aims in this program is to distinguish each phenomenon by its own properties and key parameters. We optimized the threshold values of the key parameters such as the area and darkness of the transiently darkening features in Hα −0.8 Å so that the computer can reasonably identify surges and filament activations. In comparison, for a 7-day observation period, the number of dark events detected by the program contains 89% of the events recognized visually. However, 10 times more events are detected automatically. The missing events are mainly caused by the deletion of data with poor visibility. It is found that the dark events can be identified with more precise starting and ending times by a machine than by a human. Some statistical studies of surges or other activities can be carried out based on the computer-produced database. With some modifications the program can be applied to monitor real-time dynamic features on disk, including flare ribbons. Title: Magnetic Neutral Line Rotations in Flare-Productive Regions Authors: Ishii, Takako T.; Asai, Ayumi; Kurokawa, Hiroki; Takeuchi, Tsutomu T. Bibcode: 2005HiA....13..138I Altcode: We studied what is the common magnetic field configuration among flare-productive active regions. In our previous studies we have found that the magnetic neutral line shows a rotational motion in a delta-type sunspot group NOAA 9026 where three X-class flares successively occurred. In this paper we show another examples of magnetic neutral line rotations in flare-productive sunspot groups. During the current solar maximum (cycle 23) we studied the evolution of all the active regions that have produced at least one X-class flare and have been observed by the Solar and Heliospheric Observatory (SOHO) / Michelson Doppler Imager (MDI). We examined 32 active regions from 1996 through 2002 and found that the rotational sunspot motions are common to these flare-productive active regions (e.g. vortex-like motions in NOAA 8210 9236; rotation of magnetic neutral line of delta-type sunspots in NOAA 9026 9393 9415 9591 9661 0039). These motions suggest that the emergence of twisted magnetic flux bundles are the energy source for strong flares. We discuss the relation between the magnetic helicity and such a motion of magnetic neutral line e.g. the hemisphere rule of helicity sign and the orientation of neutral line rotation. Title: Flare ribbon expansion and energy release rate Authors: Asai, Ayumi; Shimojo, Masumi; Yokoyama, Takaaki; Masuda, Satoshi; Kurokawa, Hiroki; Shibata, Kazunari Bibcode: 2005ARAOJ...7....7A Altcode: No abstract at ADS Title: Studies on the Flare Energy Build-Up Process Using SolarB/Solar Optical Telescope (SOT) and Solar Magnetic Activity Research Telescope (SMART) at Hida Observatory Authors: Ishii, T. T.; Nagata, S.; Ueno, S.; Kitai, R.; Kurokawa, H.; SMART Team Bibcode: 2004ASPC..325..331I Altcode: Evolution of active regions is one of the key topics for understanding the energy storage and triggering mechanisms of flares. In our previous studies, we found that the twisted structure of emerging magnetic flux bundles is the essential feature of flare-productive active regions. Vector magnetic field data sets are necessary to examine the twisted magnetic field structures (e.g. shear and helicity). The SolarB/Solar Optical Telescope (SOT) enables us to study the detailed magnetic field configuration with a high spatial resolution. Recently we have constructed our new telescope, Solar Magnetic Activity Research Telescope (SMART) at Hida Observatory. Vector magnetic field telescope of SMART has a much wider field of view (FOV) than that of SOT. In this paper, we propose an observational plan of the active region evolution and flare energy build-up process with SOT and SMART. Title: Transition Region Downflows in the Impulsive Phase of Flares Authors: Kamio, S.; Kurokawa, H.; Brooks, D. H. Bibcode: 2004ESASP.575..479K Altcode: 2004soho...15..479K No abstract at ADS Title: The Red-Asymmetry Distribution at Hα Flare Kernels Observed in the 2001 April 10 Solar Flare Authors: Asai, A.; Ichimoto, K.; Shibata, K.; Kitai, R.; Kurokawa, H. Bibcode: 2004AGUFMSH13A1134A Altcode: We report a detailed examination about the evolution of the Hα flare kernels during an X2.3 solar flare which occurred on 2001 April 10. The Hα red-asymmetry, that is, the red-shifted Hα emission, is observed at almost all Hα flare kernels, during the impulsive phase of the flare. At Hα kernels nonthermal particles and/or thermal conduction precipitate into the chromospheric plasma, and this is thought to lead the downward compression of the chromospheric plasma, which is observed as the reddening of Hα emission (e.g. Ichimoto & Kurokawa 1984). We examined the evolution of the flare kernels inside the flare ribbons by using the Hα images obtained with the Domeless Solar Telescope at Hida Observatory, Kyoto University. We also examined the spatial distribution of the Hα kernels which show the red-asymmetry and their relationship with the intensity of the Hα kernels. We found that the stronger the red-asymmetry is, the brighter the Hα kernel is. Then, we compared the strengthes of the Hα red-asymmetry at hard X-ray emitting sources with those at the Hα kernels without the hard X-ray emissions. Title: Features of Solar Telescopes at the Hida Observatory and the Possibilities of Coordinated Observations with SolarB Authors: Ueno, S.; Nagata, S.; Kitai, R.; Kurokawa, H. Bibcode: 2004ASPC..325..319U Altcode: At the Hida observatory, two solar telescopes, Domeless Solar Telescope (DST) and Flare Monitoring Telescope (FMT), have been operated for studying solar fundamental structures and active phenomena which affect interplanetary environment. In addition, a new telescope named Solar Magnetic Activity Research Telescope (SMART) was built from 2002 through 2003 to obtain simultaneously Hα image and the vector magnetogram of the full solar disk with high spatial and temporal resolution. In this paper, we give an outline and scientific purposes of these three telescopes, with emphasis on the SMART, and discuss about possibilities of coordinated observations with SolarB. Title: Calibration of the instrumental polarization of the Domeless Solar Telescope at the Hida Observatory Authors: Kiyohara, Junko; Ueno, Satoru; Kitai, Reizaburo; Kurokawa, Hiroki; Makita, Mitsugu; Ichimoto, Kiyoshi Bibcode: 2004SPIE.5492.1778K Altcode: A new spectropolarimeter is developed at the Domeless Solar Telescope (DST) in Hida Observatory. It consists of a rotating waveplate, Wollaston prisms, and a high-dispersion spectrograph which is vertically installed at the focus of the DST. In order to realize a high-precision measurement, it is inevitable to compensate the instrumental polarization due to the DST. We observed the quiet region of the Sun, which is considered to be highly unpolarized, with and without a sheet linear polarizer or circular polarizer set at the entrance window of the telescope. The theoretical model which represents the total instrumental polarization of the DST with some characteristic parameters was calculated and compared with the observation. The model that two flat mirrors have different properties can explain the observation in 0.5% accuracy for the unpolarized light, and in 7% for the polarized light. Title: The development of filter vector magnetographs for the Solar Magnetic Activity Research Telescope (SMART) Authors: UeNo, Satoru; Nagata, Shin-ichi; Kitai, Reizaburo; Kurokawa, Hiroki; Ichimoto, Kiyoshi Bibcode: 2004SPIE.5492..958U Altcode: In recent years, it is beginning to be shown observationally and theoretically that the existence of the magnetic field is indispensable for active phenomena on the solar surface. In particular, the rotation or helicity of the magnetic field and their temporal variation are considered to be important factors which influence solar activity. In order to confirm this, it is necessary to compute vector components of the magnetic field with a higher accuracy than before. Therefore, we developed two kinds of filter-type magnetographs for the Solar Magnetic Activity Research Telescope (SMART) at Hida observatory, which allow us to observe the polarization components in sunlight with high accuracy. We use a Lyot filter in one of two sets of magnetographs. On the other hand, a tandem-typed Fabry-Perot filter is used in one more set. For these two instruments, we made the following concrete advances. 1. The method of coating of the pre-filters. 2. Special fine-anneal on the main lenses. 3. Highly accurate rotating wave-plate. 4. Simultaneous observation of two kinds of filtergrams which have orthogonally polarized light mutually by using Fabry-Perot channel. 5. Observation in four wavelengths which can suppress various errors. 6. Low apparent Doppler shift in the FOV due to the oblique incidence of the rays to the filters. 7. Large format CCD (large-sized chip, large full-well). 8. High speed data transfer interface between the CCD and PC. In this paper, we report the details of these points, the expected effect of them, and the results of initial measurements. Title: On a Surge: Properties of an Emerging Flux Region Authors: Liu, Yu; Kurokawa, Hiroki Bibcode: 2004ApJ...610.1136L Altcode: A surge event with multi-instrument and multiwavelength observations is presented. The event occurred in a surge-productive region on 2001 August 30. TRACE white-light images, Huairou vector magnetograms, and Hβ filtergrams show that this surge was closely associated with new bipoles that emerged in 1 hr. Evidence of enhanced magnetic cancellation is revealed at the footpoints of the surge where a simultaneous surge flare is shown in the Hβ line. In particular, the interesting observational results for this surge are that (1) the surge was associated with pronounced photospheric bright points near the emerging spots; (2) in vector magnetograms, during the surge ascending period, reliable transverse fields appeared between the emerging flux and the ambient fields cancelled at the base of the surge, and these fresh transverse fields disappeared after 20 minutes; (3) the preceding spots of the emerged bipoles almost disappeared in white-light images when the surge activity stopped; and (4) the TRACE UV (1550 Å) channel showed a bright surge (~105 K) well correlated with the dark Hβ surge (~103-104 K). The UV surge had a bright spike shape and spouted out along the outer edges of the Hβ surge. Similarly, the bright components in TRACE EUV (~106 K) were also located at the edges of the Hβ surge. Both the SOHO/EIT and Yohkoh/SXT observations demonstrate that the jet plasma was ejected from one footpoint of a flaring coronal loop identified during the surge. We estimate the magnetic energy released from the site of the magnetic cancellation, the kinetic energy of the surge, and the thermal energy for the loop brightening in SXR, finding that the magnetic reconnection could supply enough energy for the surge activities and the coronal loop heating. For this surge, all the correlated phenomena in multiwavelengths (Hβ, white light, UV, EUV, and SXR) are in good temporal and spatial relationship. These facts support a magnetic reconnection model in which surges originate in the low atmosphere. Moreover, low-altitude magnetic reconnections can result in the magnetic cancellation observed on the photosphere. Title: Hida Domeless Solar Telescope and SOHO Coronal Diagnostic Spectrometer Observations of Short-Duration Active Region Blinkers. II. Extreme-Ultraviolet Properties Authors: Brooks, D. H.; Kurokawa, H. Bibcode: 2004ApJ...611.1125B Altcode: No abstract at ADS Title: Flare Ribbon Expansion and Energy Release Rate Authors: Asai, Ayumi; Yokoyama, Takaaki; Shimojo, Masumi; Masuda, Satoshi; Kurokawa, Hiroki; Shibata, Kazunari Bibcode: 2004ApJ...611..557A Altcode: We have examined the relation between the evolution of the Hα flare ribbons and the released magnetic energy in a solar flare that occurred on 2001 April 10. Based on the magnetic reconnection model, the released energy was quantitatively calculated by using the photospheric magnetic field strengths and separation speeds of the fronts of the Hα flare ribbons. We compared the variation of the released energy with the temporal and spatial fluctuations in the nonthermal radiation observed in hard X-rays and microwaves. These nonthermal radiation sources indicate when and where large energy releases occur. We also estimated the magnetic energy released during the flare. The estimated energy release rates in the Hα kernels associated with the hard X-ray sources are locally large enough to explain the difference between the spatial distributions of the Hα kernels and the hard X-ray sources. We also reconstructed the peaks in the nonthermal emission by using the estimated energy release rates. Title: Filament Oscillations and Moreton Waves Associated with EIT Waves Authors: Okamoto, Takenori J.; Nakai, Hidekazu; Keiyama, Atsushi; Narukage, Noriyuki; UeNo, Satoru; Kitai, Reizaburo; Kurokawa, Hiroki; Shibata, Kazunari Bibcode: 2004ApJ...608.1124O Altcode: In this paper we compare EUV Imaging Telescope (EIT) waves with simultaneous phenomena seen in Hα in order to address the question of what an EIT wave is. We surveyed the events associated with solar flares larger than GOES M-class in 1999-2002. The Hα data are taken with the Flare-monitoring Telescope (FMT) at the Hida Observatory of Kyoto University. Among 14 simultaneous observations of EIT waves and Hα, 11 were found to have filament eruptions, three were associated with Moreton waves, and one was found to have only filament oscillations. This shows that we cannot see clear wave fronts in Hα even if EIT waves exist, but that it is possible to recognize invisible waves by means of filament oscillations. The nature of filament oscillations and Moreton waves associated with EIT waves is examined in detail, and it is found that the filament oscillations were caused by EIT waves. Title: Formation of Opposite-Sign Magnetic Helicity by an Erupting Filament in a Coronal Mass Ejection Authors: Liu, Yu; Kurokawa, Hiroki Bibcode: 2004PASJ...56..497L Altcode: It is unclear whether it is possible for magnetic helical fields of opposite signs to co-exist in a coronal mass ejection (CME). During filament eruption with high-cadence observations for the initial stage, evidence is found for the formation of right-handed helical fields in a rising dextral filament that is embedded in a CME with helical fields in a left-handed sense. The data include Mees multi-off-band Hα observations with 16s cadence and TRACE 1600Å observations of 2s cadence. The filament material is ejected outward and is associated with the expanding CME, suggesting that both of the opposite-sign helical fields are injected into interplanetary space. In this paper, we consider the key observational features, including the formation of a coil-like structure (due to barb reconnections) and the alignment of reconnected field lines with the primary axis of the filament. It is found that they are consistent with the predicted changes during filament eruption by the filament model of Martin and McAllister. However, our results do not reject the filament model of Rust and Kumar. Moreover, a model that reconciles both of them seems to be more convenient for understanding the complicated observations. Therefore, the formation of opposite-sign helicity in an eruptive flux rope should be common for such types of filament eruptions. Title: X-Ray Expanding Features Associated with a Moreton Wave Authors: Noriyuki, Narukage; Morimoto, Taro; Kadota, Miwako; Kitai, Reizaburo; Kurokawa, Hiroki; Shibata, Kazunari Bibcode: 2004PASJ...56L...5N Altcode: No abstract at ADS Title: Short-Duration Active Region Brightenings Observed in the Extreme Ultraviolet and Hα by the Solar and Heliospheric Observatory Coronal Diagnostic Spectrometer and Hida Domeless Solar Telescope Authors: Brooks, D. H.; Kurokawa, H.; Kamio, S.; Fludra, A.; Ishii, T. T.; Kitai, R.; Kozu, H.; Ueno, S.; Yoshimura, K. Bibcode: 2004ApJ...602.1051B Altcode: We present the first detection of an Hα counterpart to the EUV blinker. The observations come from a coordinated campaign between the Hida Observatory Domeless Solar Telescope (DST) and the Solar and Heliospheric Observatory Coronal Diagnostic Spectrometer (CDS) conducted in 2002 July and August. Utilizing studies designed for high-cadence observations, many short-duration brightenings (<3 minutes) were identified in the He I λ584.334 and O V λ629.732 spectral lines in CDS data of active region NOAA 10039/10044. These brightenings show similar characteristics (increases in intensity, size) to longer duration EUV blinkers previously reported in active regions and the quiet Sun. Focusing on two events that show pronounced emission in the upper chromosphere (He I), we have been able to identify cospatial bright points in the lower chromosphere (Hα center, +/-0.5 Å) that show enhanced emission during the EUV blinker. These bright features have lifetimes similar to those of their EUV counterparts, and their peak intensities occur nearly simultaneously with the peak blinker intensities in the He I and O V lines. In both cases the He I and O V lines show excess line broadening at the peak of the event (>15 km s-1). Our high-cadence observations also enabled us to examine the dimensions and lifetimes of short-duration active region blinkers in detail. We find that the instrumental spatial and temporal resolution can combine to distort their characteristics: even short-duration blinkers appear to be composed of elementary brightening events. The optical brightenings also appear to closely follow the behavior of the elementary brightenings. The spatial and temporal relationships between the brightenings indicate a causal link between the EUV and Hα blinkers. Title: Short Duration Active Region Brightenings Observed in the EUV and Ha by SOHO/CDS and HIDA/DST Authors: Brooks, D. H.; Kurokawa, H.; Kamio, S.; Fludra, A.; Ishii, T. T.; Kitai, R.; Kosu, H.; Ueno, S.; Yoshimura, K. Bibcode: 2004ESASP.547..273B Altcode: 2004soho...13..273B We present the 1st detection of an H counterpart to the EUV blinker, using observations from a coordinated campaign between the SOHO Coronal Diagnostic Spectrometer and the Kyoto University Hida Observatory, Domeless Solar Telescope (DST). The observations were performed during July and August 2002. By designing the CDS observing sequences for high cadence and long duration observations, we were able to identify many short duration (<3 mins.) brightenings simultaneously in the He I 584.334A and O V 629.732A spectral lines. These brightenings show similar characteristics (intensity increases, sizes) to longer duration EUV blinkers previously reported in active regions and the 'quiet' Sun. Focusing on two events which show pronounced emission in the upper chromosphere (He I), we have been able to identify cospatial bright points in the lower chromosphere (H line centre, 60.5A) which show enhanced emission during the EUV blinkers. These bright features have similar lifetimes to their EUV counterparts and their peak intensities occur close to simultaneously with the peak blinker intensities in the He I and O V lines. In both cases the He I and O V lines show excess line broadening at the peak of the event (>15 km s01) and in one event evidence of downward (red-shifted) motion is observed. A statistical study is being performed to provide a complete picture of the line width and velocity characteristics of these events and to determine whether the H counterparts are common, or confined to specific blinkers with pronounced He I emission. The high cadence of our observations also allowed us to examine the eects of spatial and temporal averaging on the determination of the properties of blinkers. We find that both short and long duration blinkers are composed of elementary brightening events and that such events can be undetectable in observations with low temporal cadence. Finally, the H brightenings appear to correlate well with the elementary EUV brightening events. Title: Twisted Magnetic Flux Bundle Models for Solar Flares Authors: Ishii, T. T.; Kurokawa, H.; Takeuchi, T. T. Bibcode: 2004IAUS..219..693I Altcode: 2003IAUS..219E..79I We studied what is the key process to trigger the major solar flares using observational data of the evolutions of active regions. In our previous studies we have pointed out that the process of magnetic shear development is important for studying the above topic. We have constructed schematic models of emerging magnetic flux bundles to explain observed sunspot proper motions and found that the emergence of twisted magnetic flux bundles relates to strong flare activities in several sunspot groups. During the current solar maximum (cycle 23) we studied the evolution of all the active regions that have produced at least one X-class flare and have been observed by the Solar and Heliospheric Observatory (SOHO) / Michelson Doppler Imager (MDI). In this paper we analyzed 32 active regions from 1996 through 2002 and studied what is the the common magnetic field configuration among these active regions. We found that the above-mentioned relation between sunspot proper motions resulting from the emergence of twisted magnetic flux tubes and strong flare activities are common among flare-productive active regions. This result suggests that the emergence of twisted magnetic flux bundles are the energy source for strong flares. Title: Moreton waves observed at Hida Observatory Authors: Narukage, Noriyuki; Eto, Shigeru; Kadota, Miwako; Kitai, Reizaburo; Kurokawa, Hiroki; Shibata, Kazunari Bibcode: 2004IAUS..223..367N Altcode: 2005IAUS..223..367N Moreton waves are flare-associated waves observed to propagate across the solar disk in Halpha, especially in the wing of Halpha. The Flare Monitoring Telescope at Hida Observatory of Kyoto University observed 12 events associated with flare waves (i.e., Moreton waves and/or filament oscillations) in Halpha from 1997 to 2002. We review our studies of Moreton waves based on these observations; relation between EIT wave and Moreton wave (Eto et al. 2002),simultaneous observation with X-ray wave (Narukage et al. 2002),three dimensional structure of flare-associated wave (Narukage et al. 2004),relation between Moreton waves and filament eruptions. Title: Twisted Flux Rope Model for a Flare-productive Sunspot Group NOAA 10486 Authors: Ishii, T. T.; Kurokawa, H.; Dun, J. P.; Saito, S.; Takeuchi, T. T. Bibcode: 2004cosp...35.2412I Altcode: 2004cosp.meet.2412I What is the common magnetic field configuration among flare-productive active regions? In our previous studies, we have found that the magnetic neutral line shows a rotational motion in a δ-type active region NOAA 9026, where three X-class flares have occurred successively. During the current solar maximum (cycle 23), we studied the evolution of all active regions that have produced at least one X-class flare and have been observed by SOHO/MDI magnetograms. Active region NOAA 10486 is the most flare-productive region during this solar cycle, which have produced seven X-class flares including X28 flare on Nov. 4, 2003. We studied the formation process of δ-type magnetic configuration using SOHO/MDI magnetograms. We also studied the evolution of magnetic shear and Hα filaments using vector magnetograms obtained at Huairou Solar Observing Station and Hα images obtained with the Sartorius telescope at Kwasan Observatory, Kyoto University. In this active region, we found that a development of a strong magnetic shear with a new magnetic flux emergence along a magnetic neutral line plays an important role as the trigger of the X-class flare on Oct. 28. Based on these observational characteristics, we discuss the model of emerging bundles of a magnetic flux rope and its causal relation to the trigger of strong flares. Title: Evolution of Blue-Shifted Ha Grains Observed in the Cell Interior Authors: Kamio, S.; Kurokawa, H. Bibcode: 2004ESASP.547..143K Altcode: 2004soho...13..143K H grains are small features of strong upward motions in the chromosphere, which are seen as small dark features in the filter image centered at H blue wing. They are found ubiquitously in the interiors of network cells in the quiet region and their typical size and duration are 1000km and 1 min respectively. We obtained H filter images and H spectra simultaneously in the quiet region with Domeless Solar Telescope(DST) at Hida Observatory, Kyoto University. Sequential data of 80 min in good seeing condition allows us to study the temporal evolution of H grains in detail. Our analysis of H spectra shows that the grains appeared repetitively at the same location with interval of 3 min, which means that the generation of grains are closely related to the chromospheric oscillation. The line broadening preceding the upward motion of grains suggests that the grains are produced or triggered by the shock in the chromosphere. Chromospheric grains have been observed in other lines such as Ca II H and K, and their characteristics are summarized in the excellent review of [1]. H and Ca II grains are supposed to be the different aspect of the same phenomena. The relation between grains of H and other lines should be studied to determine the origin of chromospheric grains. Title: The Three-Dimensional Velocity Fields Of Solar Disappearing Filaments And Their Relations To Coronal Activities Authors: Morimoto, T.; Kurokawa, H. Bibcode: 2003AGUFMSH22B..03M Altcode: Solar filament disappearance (Disparition Brusque: DB) is often accompanied by a great magnetic activities such as flares and transient shock waves on and near the solar surface as well as enormous disturbances in interplanetary space due to the associated coronal mass ejection (CMEs). Thus, DBs are of great interest not only to solar physics research, but also to space science, and solar-terrestrial study. Since it is impossible to measure the velocity field of DBs with ordinal observations in the Hα line center alone, most previous studies have focused on the morphological signatures of DBs. In order to obtain the physical characteristics of DBs and relate them to other active phenomena, much effort is put into the calculation of their three-dimensional (3-D) velocity fields. Using the Hα line center, blue and red wing (Hα +/- 0.8 Å ) images obtained by the Flare Monitoring Telescope (FMT) at Hida Observatory, Kyoto University, and based on the Beckers' cloud model, we developed a new method to obtain the line-of-sight velocity of disappearing solar filaments. The line-of-sight velocity is obtained (i) by calculating the Hα line profile of the filament, and (ii) by measuring the Doppler shift which best fits the observed temporal variations of contrasts of the filament. The tangential velocity is obtained by tracing the motions of internal structures on successive images, and both line-of-sight and tangential velocities are combined to yield the 3-D velcoty field of DBs. In this method, corrections for the effective filter bandwidths of the instrument, stray light and Doppler brightening effect, are performed. Using the 3-D velocity field of DBs, we also developed a method to judge whether the DB was ejected into interplanetary space (eruptive) or remained in the corona (quasi-eruptive). The type of DBs are compared with the type of the associated coronal activites such as arcade formations observed in soft X-rays and EUV, CMEs and we conclude that the calculation of the three dimensional vector trajectories of disappearing filaments with our method can enhance the quality of space weather forecast and improve its accuracy. Title: Eruptive and Quasi-Eruptive Disappearing Solar Filaments and Their Relationship with Coronal Activities Authors: Morimoto, Taro; Kurokawa, Hiroki Bibcode: 2003PASJ...55.1141M Altcode: By measuring the 3-D velocity fields of 35 disappearing filaments (Disparition Brusques: DBs) on the solar disk, we studied the causal relationship between the motions of Hα DBs and the associated coronal phenomena. Using the derived 3-D velocity fields of the DBs, we developed a method to judge whether a DB is ejected into interplanetary space or whether it remains in the solar atmosphere. We compared the DB type thus obtained with the presence of coronal mass ejections (CMEs) and other associated coronal activities. It is inferred that eruptive filaments are always followed by the formation of arcades, while most quasi-eruptive events are followed by localized changes in soft X-rays and the EUV. A close causal relation between eruptive filaments and CMEs was also found: of 15 DBs for which Solar and Heliospheric Observatory Large Angle and Spectrometric Coronagraph data were available, all eight of the eruptive ones were associated with CMEs, while no CMEs were found following any of the 7 quasi-eruptive ones. These observational results indicate that the motions of Hα disappearing filaments are causally related to the associated coronal activities and also to the appearance of CMEs, and that an accurate analysis of their 3-D velocities is important not only for a better understanding of their acceleration and heating mechanisms, but also for predicting the occurrence of CMEs and geomagnetic storms. Title: A study of the causal relationship between the emergence of a twisted magnetic flux rope and a small Hα two-ribbon flare Authors: Brooks, D. H.; Kurokawa, H.; Yoshimura, K.; Kozu, H.; Berger, T. E. Bibcode: 2003A&A...411..273B Altcode: We present results from an analysis of a small two-ribbon flare which occurred above emerging flux in solar active region NOAA 8218 on 1998, May 13th and which was observed by the Swedish Vacuum Solar Telescope (SVST) on the island of La Palma, Spain. The relatively simple magnetic morphology and small size of the flare together with the high quality of the SVST observations allow us to examine the essential properties of flares in emerging flux regions in greater detail than before.

In this paper we compare and contrast the flaring emerging flux region simultaneously with a non-flaring emerging flux region within the same field of view. Unusual magnetic footpoint motions are observed in the flaring region, coincident with the Hα kernels, which result in a high level of shearing of the magnetic neutral line between opposite polarities. The Hα images show dark filament structures which form an inverted S-like shape immediately prior to the flare and then separate after the energy release disrupts the magnetic field. We interpret the motions and structures as strong evidence for the emergence of a twisted magnetic flux rope which developed a sheared configuration with the overlying magnetic field. In contrast the companion region shows separating footpoints, with apparent arch-like filament connections in the Hα images, consistent with the expected appearance of emerging flux. The observations imply that the attachment of the inverted S-shaped structure may be an observational consequence of the magnetic reconnection or untwisting of the field which triggered the flare. We also find some evidence that the increase in magnetic flux is faster in the flaring region.

Finally, we propose a simple schematic model of the emergence of a twisted magnetic flux rope and attached branch which can account for the observed footpoint motions and Hα structures of the flaring region. Such a model can, in principle, induce partial magnetic reconnection in the overlying coronal field and we found some evidence of coronal loop footpoint brightenings which support our conclusions. Our high resolution study supports the results of previous authors that even a small twisted structure in an emerging flux tube can be important for flare production. Title: Evolution of Flare Ribbons and Energy Release Authors: Asai, A.; Yokoyama, Takaaki; Shimojo, Masumi; Masuda, Satoshi; Kurokawa, Hiroki; Shibata, Kazunari Bibcode: 2003ICRC....6.3367A Altcode: 2003ICRC...28.3367A We examined the relation between evolutions of flare ribb ons and released magnetic energies at a solar flare which occurred on 2001 April 10 in the active region NOAA 9415. We successfully evaluated the released energy quantitatively, based on the magnetic reconnection model. We measured the photospheric magnetic field strengths and the separation speeds of the fronts of the Hα flare ribb on, and estimated the released magnetic energy at the flare by using those values. Then, we compared the estimated energy release rates with the nonthermal behaviors observed in hard X-rays and microwaves. We found that those at the Hα kernels associated with the HXR sources are locally large enough to explain the difference between the spatial distribution the Hα kernels and the hard X-ray sources. Their temporal evolution of the energy release rates also shows peaks corresponding to hard X-ray bursts. Title: Precise determination of cooling times of post-flare loops from the detailed comparison between Hα and soft X-ray images Authors: Kamio, Suguru; Kurokawa, Hiroki; Ishii, Takako T. Bibcode: 2003SoPh..215..127K Altcode: A detailed study of the evolution and cooling process of post-flare loops is presented for a large X9.2 solar flare of 2 November 1992 by using Hα images obtained with Domeless Solar Telescope at Hida Observatory and soft X-ray images of Yohkoh Soft X-ray Telescope (SXT). The detailed analysis with a new method allows us to determine more precise values of the cooling times from 107 K to 104 K plasma in the post-flare loops than in previous works. The subtraction of sequential images shows that soft X-ray dimming regions are well correlated to the Hα brightening loop structure. The cooling times between 107 K and 104 K are defined as the time difference between the start of soft X-ray intensity decrease and the end of Hα intensity increase at a selected point, where the causal relation between Hα brightening and soft X-ray dimming loops is confirmed. The obtained cooling times change with time; about 10 min at the initial stage and about 40 min at the later stage. The combined conductive and radiative cooling times are also calculated by using the temperature and density obtained from SXT data. Calculated cooling times are close to observed cooling times at the beginning of the flare and longer in the later stage. Title: A Method for the Determination of 3-D Velocity Fields of Disappearing Solar Filaments Authors: Morimoto, Taro; Kurokawa, Hiroki Bibcode: 2003PASJ...55..503M Altcode: 2003PASJ...55..505M The 3-D velocity fields of disappearing filaments (Disparition Brusques: DBs) on the solar disk were extensively studied in order to determine their 3-D velocity fields. Applying Beckers' cloud model to 5 DB events observed in the Hα line center and Hα ± 0.8 Å with the Flare Monitoring Telescope (FMT) at Hida Observatory, we developed a method to derive the complete 3-D velocity field of DBs. The line-of-sight velocity is obtained (i) by calculating the Hα line profile of the filament, and (ii) by measuring the Doppler shift which best fits to the observed temporal variations of contrasts of the filament. The tangential velocity is obtained by tracing the motions of the internal structures on the successive images. In this method, corrections for the effective filter bandwidths of the instrument, stray lights, and Doppler brightening effect are performed. We also discuss the velocity errors which arise from the intrinsic variations of the filament plasma during its activation, the fluctuations in intensities of the background chromosphere, and the choice of different forms of the spread function for estimating the stray light. It is emphasized that the calculation of three-dimensional vector trajectories of a disappearing filament with our method can enhance the quality of a space weather forecast with better certainty. Title: Evolution of Conjugate Footpoints inside Flare Ribbons during a Great Two-Ribbon Flare on 2001 April 10 Authors: Asai, Ayumi; Ishii, Takako T.; Kurokawa, Hiroki; Yokoyama, Takaaki; Shimojo, Masumi Bibcode: 2003ApJ...586..624A Altcode: We report a detailed examination of the fine structure inside flare ribbons and the temporal evolution of such structure during an X2.3 solar flare, which occurred on 2001 April 10. We examined fine structures, such as systems of conjugate footpoints, inside flare ribbons by using the Hα images obtained with the Sartorius telescope at Kwasan Observatory, Kyoto University. We identified the conjugate footpoints of each Hα kernel in both flare ribbons by a new method that uses cross-correlation functions of the light curves. We also compared the sites of the Hα kernels with the spatial configurations of flare loops seen in the extreme-ultraviolet images obtained with the Transition Region and Coronal Explorer. We found that the highly correlated pairs of Hα kernels were connected by flare loops seen in the 171 Å images. Investigating such fine structures inside the flare ribbons, we can follow the history of energy release and perhaps acquire key information about particle acceleration. Title: Close Correlation among Hα Surges, Magnetic Flux Cancellations, and UV Brightenings Found at the Edge of an Emerging Flux Region Authors: Yoshimura, Keiji; Kurokawa, Hiroki; Shimojo, Masumi; Shine, Richard Bibcode: 2003PASJ...55..313Y Altcode: Surge activities were observed at the edge of an emerging flux region. We studied the relations between the features around the surges in various data sets: magnetogram, Hα, G-band, UV, EUV, and soft X-rays. We showed that the surge activities in Hα and the brightenings in TRACE 1600Å images correlate well in both time and space with the cancellation of magnetic fluxes around an emerging flux region. In particular, at the onset of surge activity, a close correlation among them was clearly found. These facts are consistent with the magnetic reconnection model. The released energy through magnetic reconnection, which is estimated to be 1028 erg, is sufficiently large to produce surge activities. No prominent brightenings were observed in soft X-ray and EUV images during the surge activities. This may suggest that the energy releases occurred at a layer of high densities. Title: Evolution of flare ribbons and energy release Authors: Asai, A.; Masuda, S.; Yokoyama, T.; Shimojo, M.; Kurokawa, H.; Ishii, T. T.; Shibatal, K. Bibcode: 2003AdSpR..32.2561A Altcode: We examined the relation between the evolutions of the H α flare ribbons and the released magnetic energiesat a solar flare which occurred on 2001 April 10. This is the first study to evaluate the released energy quantitatively, based on the magnetic reconnection model, and by using the data obtained with the multi wavelength observation. We measured the, photospheric magnetic field strengths and the separation speeds of the fronts of the H α flare ribbon, and compared them the nonthermal behaviors observed in HXRs and microwaves. Those nonthermal radiation sources tell us when and where large energy releases occur. Then, by using the photospheric and chromospheric features, we estimated the released magnetic energy at the flare. The estimated energy release rates at the H α kernels associated with the HXR sources are locally large enough to explain the difference between the spatial distribution the H α kernels and the HXR sources. Their temporal evolution of the energy release rates also shows peaks corresponding to HXR bursts. Title: Magnetic Neutral Line Rotations in Flare-Productive Regions Authors: Ishii, Takako T.; Asai, Ayumi; Kurokawa, Hiroki; Takeuchi, Tsutomu T. Bibcode: 2003IAUJD...3E..15I Altcode: We studied what is the common magnetic field configuration among flare-productive active regions. In our previous studies we have found that the magnetic neutral line shows a rotational motion in a delta-type sunspot group NOAA 9026 where three X-class flares successively occurred. In this paper we show another examples of magnetic neutral line rotations in flare-productive sunspot groups. During the current solar maximum (cycle 23) we studied the evolution of all the active regions that have produced at least one X-class flare and have been observed by the Solar and Heliospheric Observatory (SOHO) / Michelson Doppler Imager (MDI). We examined 32 active regions from 1996 through 2002 and found that the rotational sunspot motions are common to these flare-productive active regions (e.g. vortex-like motions in NOAA 8210 9236; rotation of magnetic neutral line of delta-type sunspots in NOAA 9026 9393 9415 9591 9661 0039). These motions suggest that the emergence of twisted magnetic flux bundles are the energy source for strong flares. We discuss the relation between the magnetic helicity and such a motion of magnetic neutral line e.g. the hemisphere rule of helicity sign and the orientation of neutral line rotation Title: Difference between Spatial Distributions of the Hα Kernels and Hard X-Ray Sources in a Solar Flare Authors: Asai, Ayumi; Masuda, Satoshi; Yokoyama, Takaaki; Shimojo, Masumi; Isobe, Hiroaki; Kurokawa, Hiroki; Shibata, Kazunari Bibcode: 2002ApJ...578L..91A Altcode: 2002astro.ph..9106A We present the relation of the spatial distribution of Hα kernels with the distribution of hard X-ray (HXR) sources seen during the 2001 April 10 solar flare. This flare was observed in Hα with the Sartorius telescope at Kwasan Observatory, Kyoto University, and in HXRs with the hard X-ray telescope (HXT) on board Yohkoh. We compared the spatial distribution of the HXR sources with that of the Hα kernels. While many Hα kernels are found to brighten successively during the evolution of the flare ribbons, only a few radiation sources are seen in the HXR images. We measured the photospheric magnetic field strengths at each radiation source in the Hα images and found that the Hα kernels accompanied by HXR radiation have magnetic strengths about 3 times larger than those without HXR radiation. We also estimated the energy release rates based on the magnetic reconnection model. The release rates at the Hα kernels with accompanying HXR sources are 16-27 times larger than those without HXR sources. These values are sufficiently larger than the dynamic range of HXT, which is about 10, so that the difference between the spatial distributions of the Hα kernels and the HXR sources can be explained. Title: The Large-Scale Coronal Field Structure and Source Region Features for a Halo Coronal Mass Ejection Authors: Wang, Tongjiang; Yan, Yihua; Wang, Jialong; Kurokawa, H.; Shibata, K. Bibcode: 2002ApJ...572..580W Altcode: On 1998 May 2 a class X1/3B flare occurred at 13:42 UT in NOAA Active Region 8210 near disk center, which was followed by a halo coronal mass ejection (CME) at 15:03 UT observed by SOHO/LASCO. Using the boundary element method (BEM) on a global potential model, we reconstruct the large-scale coronal field structure from a composite boundary by SOHO/MDI and Kitt Peak magnetograms. The extrapolated large field lines well model a transequatorial interconnecting loop (TIL) seen in the soft X-ray (SXR) between AR 8210 and AR 8214, which disappeared after the CME. The EUV Imaging Telescope (EIT) observed the widely extending dimmings, which noticeably deviate from the SXR TIL in position. We find that the major dimmings are magnetically linked to the flaring active region but some dimmings are not. The spatial relationships of these features suggest that the CME may be led by a global restructuring of multipolar magnetic systems due to flare disturbances. Mass, magnetic energy, and flux of the ejected material estimated from the dimming regions are comparable to the output of large CMEs, derived from the limb events. At the CME source region, Huairou vector magnetograms show that a strong shear was rapidly developed in a newly emerging flux region (EFR) near the main spot before the flare. Magnetic field extrapolations reveal the presence of a ``bald patch'' (defined as the locations where the magnetic field is tangent to the photosphere) at the edge of the EFR. The preflare features such as EUV loop brightenings and SXR jets appearing at the bald patch suggest a slow reconnection between the TIL field system and a preexisting overlying field above the sheared EFR flux system. High-cadence Yohkoh/SXT images reveal a fast expanding motion of loops above a bright core just several minutes before the hard X-ray onset. This may be a precursor for the eruption of the sheared EFR flux to produce the flare. We propose a scenario, similar to the ``breakout'' model in principle, that can interpret many observed features. Title: Relation between a Moreton Wave and an EIT Wave Observed on 1997 November 4 Authors: Eto, Shigeru; Isobe, Hiroaki; Narukage, Noriyuki; Asai, Ayumi; Morimoto, Taro; Thompson, Barbara; Yashiro, Seiji; Wang, Tongjiang; Kitai, Reizaburo; Kurokawa, Hiroki; Shibata, Kazunari Bibcode: 2002PASJ...54..481E Altcode: We consider the relationship between two flare-associated waves, a chromospheric Moreton wave and a coronal EIT wave, based on an analysis of an X-class flare event in AR 8100 on 1997 November 4. A Moreton wave was observed in Hα + 0.8 Å, and Hα - 0.8 Å with the Flare-Monitoring Telescope (FMT) at the Hida Observatory. An EIT wave was observed in EUV with the Extreme ultraviolet Imaging Telescope (EIT) on board SOHO. The propagation speeds of the Moreton wave and the EIT wave were approximately 715 km s-1 and 202 km s-1, respectively. The times of visibility for the Moreton wave did not overlap those of the EIT wave, but the continuation of the former is indicated by a filament oscillation. Data on the speed and location clearly show that the Moreton wave differed physically from the EIT wave in this case. The Moreton wave preceded the EIT wave, which is inconsistent with an identification of the EIT wave with a fast-mode MHD shock. Title: Simultaneous Observation of a Moreton Wave on 1997 November 3 in Hα and Soft X-Rays Authors: Narukage, N.; Hudson, H. S.; Morimoto, T.; Akiyama, S.; Kitai, R.; Kurokawa, H.; Shibata, K. Bibcode: 2002ApJ...572L.109N Altcode: We report the observation of a Moreton wave in Hα (line center and +/-0.8 Å) with the Flare Monitoring Telescope at the Hida Observatory of Kyoto University at 4:36-4:41 UT on 1997 November 3. The same region (NOAA Active Region 8100) was simultaneously observed in soft X-rays with the soft X-ray telescope on board Yohkoh, and a wavelike disturbance (``X-ray wave'') was also found. The position of the wave front as well as the direction of propagation of the X-ray wave roughly agree with those of the Moreton wave. The propagation speeds of the Moreton wave and the X-ray wave are about 490+/-40 and 630+/-100 km s-1, respectively. Assuming that the X-ray wave is an MHD fast-mode shock, we can estimate the propagation speed of the shock, on the basis of MHD shock theory and the observed soft X-ray intensities ahead of and behind the X-ray wave front. The estimated fast shock speed is 400-760 km s-1, which is in rough agreement with the observed propagation speed of the X-ray wave. The fast-mode Mach number of the X-ray wave is also estimated to be about 1.15-1.25. These results suggest that the X-ray wave is a weak MHD fast-mode shock propagating through the corona and hence is the coronal counterpart of the Moreton wave. Title: Emergence and Drastic Breakdown of a Twisted Flux Rope to Trigger Strong Solar Flares in NOAA Active Region 9026 Authors: Kurokawa, Hiroki; Wang, Tongjiang; Ishii, Takako T. Bibcode: 2002ApJ...572..598K Altcode: An emerging twisted flux rope model to explain the drastic evolution of a flare-productive NOAA Active Region 9026 is presented. The drastic changes in the δ-type sunspot configuration were found to start shortly before the big flares of 2000 June 6: (1) rapid proper motions of sunspots started at the both sides of the central δ sunspot about 7 hr prior to the strong flare activity, (2) the collapse of the central δ sunspot with its disintegration and partial disappearance started about 3 hr before the strong flare activity, (3) a switchback-shaped and strongly sheared magnetic neutral line was formed with intruding motions of sunspots into the opposite magnetic polarities, and (4) the direction of the neutral line rapidly rotated clockwise at the same time when the switchback neutral line was formed. To explain these outstanding features of the sunspot evolution, we constructed a schematic model of an emerging twisted flux rope in which the central writhe helicity of the flux rope could be formed by continuous transformation of the twist helicity by means of the kink instability in the course of its emergence through the convection zone. Title: Dynamical Features and Evolutional Characteristics of Brightening Coronal Loops Authors: Shimojo, Masumi; Kurokawa, Hiroki; Yoshimura, Keiji Bibcode: 2002SoPh..206..133S Altcode: We present a detailed study of coronal loop brightenings observed in an active region on the solar limb. These brightening loops show expanding and shrinking motions in EUV coronal line images and also show downflow along the loops in Lα and Hα images. By means of time-slice analysis of the images, we found that both the expanding and shrinking motions of the loops are not real motions of plasma but apparent motions like post-flare loops, where the loops at the different height are successively heated and cooled. From a temperature analysis, the time delay between the brightenings of hot 195 Å and cool Lα loops is found to be nearly equal to the time-scale of the conduction cooling. We conclude that these loop brightenings are sources of so called Hα coronal rains. Title: Multi-wavelength Observations of a Moreton Wave on 2000 March 3 Authors: Narukage, N.; Morimoto, T.; Kitai, R.; Kurokawa, H.; Shibata, K. Bibcode: 2002aprm.conf..449N Altcode: Moreton waves are flare-associated waves observed to propagate across the solar disk in Hα (Moreton, 1960). Such waves have been identified as the intersections of a coronal fast-mode shock fronts and the chromosphere (Uchida, 1968). We report the observation of a Moreton wave in Hα (line center and ± 0.8 Å) with the Flare Monitoring Telescope (FMT) at the Hida Observatory of Kyoto University on 2000 March 3. The same region (NOAA 8882) was simultaneously observed in soft X-rays with the soft X-ray Telescope (SXT) on board Yohkoh, and a coronal wave-like disturbance (``X-ray wave") was also found. The region (NOAA 8882) is near the solar limb. Hence the chromospheric Moreton wave propagated on the solar disk at a speed of 1050 km/s, whereas the coronal X-ray wave propagated towards the outer corona at 1300 km/s. We identified the X-ray wave as an MHD fast-mode shock, i.e. a coronal counterpart of the Moreton wave, using MHD shock theory and the observed soft X-ray intensities (Narukage et al., 2002). On the basis of this result, the propagation of these two waves indicates the 3-dimensional structure of the flare-associated shock wave. This event is the first observation of the 3-d structure of the shock. Moreover, a type II radio burst and a coronal mass ejection (CME) were also observed simultaneously. The shock speed given by the type II radio burst is 1150 km/s. The CME propagated at a speed of 800 km/s. A basic component of CME is a density enhancement, and the shock preceding the CME propagates roughly 1.5 times faster than the CME, in this case at 1200 km/s. Title: Characteristics of flare-productive sunspot groups Authors: Ishii, Takako T.; Kurokawa, Hiroki; Takeuchi, Tsutomu T. Bibcode: 2002HiA....12..395I Altcode: No abstract at ADS Title: Evolution of Flare Ribbons and Energy Release Authors: Asai, A.; Masuda, S.; Yokoyama, T.; Shimojo, M.; Ishii, T. T.; Isobe, H.; Shibata, K.; Kurokawa, H. Bibcode: 2002aprm.conf..415A Altcode: We estimated the released magnetic energy via magnetic reconnection in the corona by using photospheric and chromospheric features. We observed an X2.3 flare, which occurred in active region NOAA9415 on 2001 April 10, in Hα with the Sartorius Telescope at Kwasan Observatory, Kyoto University. Comparing the Hα images with the hard X-ray (HXR) images obtained with Yohkoh/HXT, we see only two HXR sources which are accompanied by Hα kernels. At these Hα kernels the large energy release is thought to be larger than at other Hα kernels. We estimated the energy release rates at each Hα kernel by using the photospheric magnetic field strength and the separation speed of the Hα flare ribbons at the same location. The estimated energy release rates at the Hα kernels associated with the HXR sources are locally large enough to explain the different appearance. Their temporal evolution also shows peaks corresponding to HXR bursts. Title: Vortex-like Sunspot Proper Motions in Flare-producing Active Regions Authors: Ishii, T. T.; Kurokawa, H.; Takeuchi, T. T. Bibcode: 2002aprm.conf..431I Altcode: We studied what is the key process to trigger major solar flares using observational data of active region evolution. In our previous studies, we have examined the processes of magnetic shear development in many sunspot groups using high resolution Hα images obtained with the 60-cm Domeless Solar Telescope (DST) at Hida Observatory, Kyoto University. We have constructed schematic models of emerging magnetic flux bundles to explain observed sunspot proper motions, and found several examples of sunspot groups, where the emergence of twisted magnetic flux tubes triggered major flares. During the current solar maximum (cycle 23), we applied our method to the magnetograms obtained by the Solar and Heliospheric Observatory (SOHO)/Michelson Doppler Imager (MDI) and white light images by the Transition Region and Coronal Explorer (TRACE). In this paper, we show several examples of active regions where we found vortex-like sunspot proper motions and strong flare activities. These motions suggest that the emergence of twisted magnetic flux bundles is the energy source for strong flares. Title: Multi-Wavelength Observation of A Moreton Wave on November 3, 1997 Authors: Narukage, N.; Shibata, K.; Hudson, H. S.; Eto, S.; Isobe, H.; Asai, A.; Morimoto, T.; Kozu, H.; Ishii, T. T.; Akiyama, S.; Kitai, R.; Kurokawa, H. Bibcode: 2002mwoc.conf..295N Altcode: No abstract at ADS Title: Fine Structure inside Flare Ribbons and Temporal Evolution Authors: Asai, A.; Masuda, S.; Yokoyama, T.; Shimojo, M.; Kurokawa, H.; Shibata, K.; Ishii, T. T.; Kitai, R.; Isobe, H.; Yaji, K. Bibcode: 2002mwoc.conf..221A Altcode: Non-thermal particles generated in the impulsive phase of solar flares are observed mainly in microwave, hard X-rays, and gamma-rays. Observations in Hα can also give important informations about non-thermal particles precipitating into the chromosphere with a higher spatial resolution than in other wavelengths. We observed an X2.3 flare which occurred in the active region NOAA 9415 on 10 April 2001, in Hα with Sartorius Telescope at Kwasan Observatory, Kyoto University. Thanks to the short exposure time given for the flare, the Hα images show fine structures inside the flare ribbons. In addition to Hα, we analyze microwave, hard X-ray, and EUV data obtained with Nobeyama Radioheliograph, Yohkoh/HXT, and TRACE, respectively. In Hα, several bright kernels are observed in the flare ribbons. On the other hand, the hard X-ray images show only a single pair of bright sources which correspond to one of several pairs of Hα kernels. Examining the difference in the magnetic field strength and in the time profiles of Hα emission for these kernels, we discuss the reason why only one pair kernels are bright in the hard X-ray among the other bright Hα kernels. Comparing the Hα images with EUV images, we also examine the three-dimensional structure of solar flares. While broad and network-like ribbons are observed in Hα, the width of EUV ribbons is relatively narrow, and EUV ribbons are located at the outer edges of the corresponding Hα ribbon. Title: Evolution of flare ribbons and energy release Authors: Asai, A.; Masuda, S.; Yokoyama, T.; Shimojo, M.; Kurokawa, H.; Ishii, T.; Shibata, K. Bibcode: 2002cosp...34E1179A Altcode: 2002cosp.meetE1179A Non-thermal particles generated in the impulsive phase of solar flares are observed mainly in microwave, hard X-rays, and g amma-rays. Observations in Halpha can also give important informations about non-thermal particles precipitating into the chromosphere with a higher spatial resolution than in other wavelengths. We observed an X2.3 flare which occurred in the active region NOAA 9415 on 10 April 2001, in Halpha with the Sartorius Telescope at Kwasan Observatory, Kyoto University. Thanks to the short exposure time given for the flare, the Halpha images show fine structures inside the flare ribbons. In Halpha, several bright kernels are observed in the flare ribbons. On the other hand, the hard X-ray images show only a single pair of bright sources which correspond to one of several pairs of Halpha kernels. In this paper, we examined the magnetic field strength at each H kernel and the separation speed of the H flare ribbons, and estimated the energy release rate with the method based on the magnetic reconnection model (Isobe et al. 2002). We found that the energy release rate is well correlated with the time profiles of hard X-ray and microwave. Title: Simultaneous observations of Moreton waves in Hα and Soft X-ray Authors: Narukage, N.; Hudson, H.; Morimoto, T.; Kitai, R.; Kurokawa, H.; Shibata, K. Bibcode: 2002cosp...34E1337N Altcode: 2002cosp.meetE1337N Moreton waves are flare-associated waves observed to propagate across the solar disk in H (Moreton, 1960). Such waves have been identified as the intersections of a coronal fast-mode shock fronts and the chromosphere (Uchida, 1967). We report the two observations of Moreton waves in H (line center and +/- 0.8 A) with the Flare Monitoring Telescope (FMT) at the Hida Observatory of Kyoto University. The both events were simultaneously observed in soft X-rays with the Soft X-ray Telescope (SXT) on board Yohkoh, and wave-like disturbances ("X-ray wave") were also found. One event occurred in solar-disk on November 3, 1997, the other near solar limb on March 3, 2000. Assuming that the X-ray waves are the MHD fast shocks, we can estimate the propagation speeds of the shocks, based on the MHD shock theory and the observed soft X-ray intensities ahead and behind the X-ray wave fronts. It is found that the estimated fast shock speeds are in rough agreement with the observed propagation speeds of the X-ray waves. The fast mode Mach numbers of the X-ray waves are also estimated. These results suggest that the X-ray waves are MHD fast shocks propagating through the corona and hence are the coronal counterparts of the Moreton waves. Title: On the directions of solar filament eruptions Authors: Morimoto, T.; Asai, A.; Isobe, H.; Chen, P.; Kurokawa, H. Bibcode: 2002cosp...34E1178M Altcode: 2002cosp.meetE1178M We report on the relation between directions of solar filament eruptions and the distribution of magnetic field strengths at and near the source regions. The solar filaments and prominences become cores of coronal mass ejections (CMEs) when they are ejected into the interplanetary space. These CMEs appear as halo CMEs when directed toward the earth, and they often cause geomagnetic storms. It is, therefore, very important to know the direction of a CME before or in the initial phase of its onset. Making use of H line center, blue and red wing images, together with the Doppler method, we measured 3D velocity field of more than 15 events of solar disappearing filament (SDF). From the velocity field, we obtained the directions of these SDFs, and compared it with the distributions of photospheric magnetic field strengths. We found that both orientation angle (angle by the solar meridian and a vector of the direction of a filament projected onto the solar surface) and ejection angle (elevationangle measured against the solar surface) well match with the vector of local gradient of photospheric magnetic field strengths. The possibility to predict the direction of a CME even before its onset is also discussed. Title: Observations of Moreton Waves and EIT Waves Authors: Shibata, K.; Eto, S.; Narukage, N.; Isobe, H.; Morimoto, T.; Kozu, H.; Asai, A.; Ishii, T.; Akiyama, S.; Ueno, S.; Kitai, R.; Kurokawa, H.; Yashiro, S.; Thompson, B. J.; Wang, T.; Hudson, H. S. Bibcode: 2002mwoc.conf..279S Altcode: The Moreton wave is a flare-associated wave observed in H alpha, and is now established to be a fast mode MHD shock emitted from the flare, but the physical mechanism to create the wave is still puzzling. On the other hand, the EIT wave is a newly discovered flare-associated wave observed in EUV with the Extreme ultraviolet Imaging Telescope (EIT) aboard SOHO, and in this case, not only its origin but also its physical property are both puzzling. We study the relationship of these two flare-associated waves, Moreton waves and EIT waves, by analyzing 4 events observed on Nov. 3 and 4, 1997, Aug. 8, 1998, and Mar. 3, 2000 (Narukage et al. 2001). The Moreton waves were observed in Ha, Ha+0.8A and Ha-0.8A with the Flare Monitoring Telescope (FMT) at the Hida Observatory of Kyoto University, while the EIT waves were observed with SOHO/EIT. In the typical case associated with an X-class flare in AR 8100 on 4 November 1997 (Eto et al. 2001) the propagation speeds of the Moreton wave and the EIT wave were approximately 780 km/s and 200 km/s respectively. The data on speed and location show clearly that the Moreton wave differs physically from the EIT wave in this case. The detailed analyses of the other events (Nov. 3, 1997, Aug. 8, 1998, and Mar. 3, 2000) will also be presented, with Yohkoh/SXT data in the lucky case. Title: Flight demonstration of a superpressure balloon by three-dimensional gore design Authors: Izutsu, N.; Yajima, N.; Ohta, S.; Honda, H.; Kurokawa, H.; Matsushima, K. Bibcode: 2002AdSpR..30.1221I Altcode: On May 15, 1999, a balloon with a volume of 3,100 cubic meters was successfully launched from Sanriku Balloon Center of Japan. It became a superpressure balloon at 19.2km in altitude with 20% pressure difference to the ambient atmosphere. This is the first superpressure balloon capable of suspending a heavy payload. It was designed by the new 'three-dimensional gore design' method and was based on a pumpkin shape balloon with bulges of small radii between adjacent load tapes without the help of film extensibility. The balloon climbed up to 21.6km in altitude by dropping the ballast and held out against a 64% pressure difference over the ambient atmosphere. This flight test proved the capability of large stratospheric superpressure balloons by this new design method. Title: Pre-Flare Heating Around the Temperature Minimum Region Found Right Prior to an X-Class Flare Authors: Kurokawa, H.; Ishii, T. T.; Wang, T. J.; Shine, R. Bibcode: 2002mwoc.conf..257K Altcode: Studies of magnetic shear developments and pre-flare activities in flare-productive sunspot regions are fundamentally important for the study of flare energy build-up and energy release mechanism. Several previous works demonstrated that the emergence of a twisted magnetic flux rope, which is originally formed in the convection zone, must be the source of the strong magnetic shear development in a sunspot region to produce a strong flare activity (Kurokawa 1987, Tanaka 1991, Ishii et al. 2000). We are still, however, far from sufficiently understanding how the twisted structures of a magnetic flux rope is formed in the convection zone, and where and how such a twisted magnetic rope untwists and releases its energy as flaresNULL A flare productive active region NOAA 9026, which showed an interesting evolution during a coordinated observation between the Domeless Solar Telescope of Hida Observatory, Swedish Telescope of La Palma, and TRACE Satellite from 3 through 12 June of 2000, provided us a rare opportunity to study a new important aspect of a twisted magnetic flux rope and its rapidly-untwisted motions to have caused strong flares. From the analyses of the evolution of this region, we first found a clear evidence of pre-flare heating or energy release from the upper photosphere through the lower chromosphere from about two hours before the energy release in the corona as an X-class flare. We suggest that this pre-flare energy release in the lower atmosphere is closely related to the emergence of the twisted magnetic flux rope from below the photosphere. Title: Surges, Magnetic Flux Cancellations, and UV Brightenings around an Emerging Flux Region Authors: Yoshimura, K.; Kurokawa, H.; Shimojo, M.; Shine, R. Bibcode: 2002mwoc.conf...99Y Altcode: Surge activities, which are observed in Hα images, have been studying for a long time. Many authors noticed that cancellations of magnetic flux was an important factor for surge activities and proposed the models based on magnetic reconnection. But there are not many observations which have enough cadence for comparison changes of magnetic field with surge activities. So the correlation between surges and magnetic flux cancellations is not clear yet. (ex. Zhang et al. 2001) We studied the temporal and spatial relations between surge activities and other phenomena which may be accompanied by surge activities. The data we used here are from coordinated observation with Swedish Vacuum Solar Telescope on La Palma, TRACE and SOHO/MDI. So high cadence images for the same target are available in various wavelengths. MDI, for example, took magnetogram data every one minutes with high resolution mode at that time. The main results from this study are as follows: (1) We can not find any large time lag between the onset of the surge and of the magnetic fields cancellation. This is a conflict result against the one in Zhang et al. (2) There were UV brightenings which correlated well with rapid cancellation of magnetic fields. (3) The UV brightenings located just on neutral lines with some displacement from the region where rapid magnetic cancellation occurred. These observational fact can be explained by magnetic reconnection model. Title: Plasma Ejections from a Light Bridge in a Sunspot Umbra Authors: Asai, Ayumi; Ishii, Takako T.; Kurokawa, Hiroki Bibcode: 2001ApJ...555L..65A Altcode: 2001astro.ph.11021A We present conspicuous activities of plasma ejections along a light bridge of a stable and mature sunspot in NOAA Active Region 8971 on 2000 May 2. We found the ejections both in the Hα (104 K) images obtained with the Domeless Solar Telescope at Hida Observatory and in the 171 Å (Fe IX/Fe X; ~106 K) images obtained with the Transition Region and Coronal Explorer. Main characteristics of the ejections are as follows: (1) Ejections occur intermittently and recurrently. (2) The velocities and the timings of the 171 Å ejections are the same as those of Hα ejections. (3) The appearance of the ejections are different from one another; i.e., the Hα ejections have a jetlike appearance, while the 171 Å ejections are like loops. Title: Distribution of the Green- and Red-Line Coronal Emissions and Their Contribution to the K-Corona Authors: Takeda, A.; Kurokawa, H.; Kitai, R.; Ishiura, K. Bibcode: 2001AGUSM..SH41B06T Altcode: We have made a detailed analysis of the high-resolution images of the corona obtained during the total solar eclipse on 1991, July 11. The purpose of the analysis is to derive the temperature and density structure of the observed corona as reliable as possible by using the absolute intensities of the the green (530.3 nm) and red (637.4 nm) coronal emission lines and then contrasted to the continuum intensity. First, we focus our attention to the loops appeared distinctly in emission-line images. With the help of a structure-enhancement algorithm, we show the following results in a quantitative way. (1) The green- and red-line loops are quite separately distributed in space. (2) In the innermost corona, structures in the red-line tend to contribute more to the total column density than the green-line structures. Second, we study individual emission-line loops and find that, (1) The electron densities are almost the same between the two wavelengths. (2) Density-falls with height are nearly hydrostatic in most loops, while some red-line loops significantly deflected from the hydrostatic curve. (3) Column density of the analysed loops only explains 0.1 to 0.2 of the total column density derived from the continuum intensity at the same point. Then, we propose a method to determine the contribution of the non-loop component of these emission lines to the total column density. It is found that the total column density in the analyzed region can be reasonably explained by a mixture of the 530.3 nm component with a line-of-sight length comparable to the size of the active region, and the 637.4 nm component, which tends to concentrate in loop structures. We thereby conclude that the observed corona is well explained by plasma of temperatures ranging from 1 MK to 2 MK. Title: Active Region Evolution and Flare Activities: From the Photosphere to the Corona Authors: Ishii, T. T.; Kurokawa, H.; Takeuchi, T. T. Bibcode: 2001IAUS..203..280I Altcode: The formation process of magnetic shear is a key to understand the physical mechanism of solar flare occurrence. In order to examine such a process, we need observational data of active region evolution from the photosphere to the corona. In this paper, we study active region evolutions and its relation with flare activities, using H-alpha images obtained at Hida and Kwasan Observatories and white light images with Transition Region And Coronal Explorer (TRACE). We also use the Solar and Heliospheric Observatory (SOHO) / Michelson Doppler Imager (MDI) intensitygram and longitudinal magnetogram for investigation of photospheric structures of active regions. Coronal structures of the regions are studied by using extreme ultraviolet (EUV) images obtained with SOHO and TRACE. We investigate the evolution of the several active regions. We mainly report the evolution of the active region NOAA 8948 (April 2000) and discuss the relation between evolutionary characteristics and its flare activities. Many H-alpha sub-flares and several X-ray (C- and M-class) flares occurred in this active region. We suggest that the flares are triggered by the magnetic flux emergence that forms new sunspots in the following part of the active region. Title: Evolution of Hα fine loop structures observed in a long-duration solar flare Authors: Ishii, T. T.; Inoue, K.; Kamio, S.; Sakai, K.; Watanabe, Y.; Kurokawa, H. Bibcode: 2001AdSpR..26.1789I Altcode: We study the structure and evolution of a large X9 flare, which was observed at the Western limb on Nov. 2, 1992. We obtained high resolution Hα images with the 60 cm Domeless Solar Telescope at Hida Observatory, Kyoto University. Our data sets include the images observed just at the flare onset, so we could trace the evolution of post-flare loops from the beginning in detail. In this paper, we present co-aligned Hα (obtained at Hida Observatory) and soft X-ray (obtained with Yohkoh Soft X-ray Telescope) images and evolutions of the multiple loops. Title: Soft X-ray flares and magnetic configuration in a solar active region in February 1992 Authors: Zhang, H. Q.; Sakurai, T.; Shibata, K.; Shimojo, M.; Kurokawa, H. Bibcode: 2000A&A...357..725Z Altcode: In this paper, we examine the observational soft X-ray flares and the relationship with photospheric vector magnetograms in the active region (NOAA 7070). We analyze the soft X-ray flare on Feb. 24-25, 1992, especially the pre-flare and the relationship with the highly sheared photospheric vector magnetic field near the photospheric magnetic neutral line. We find that the initial reconnection of the magnetic field in the flare on Feb. 24-25, 1992 probably occurs near the magnetic neutral line in the lower atmosphere of the active region, where the highly sheared magnetic flux erupts up and triggers the reconnection of the large-scale magnetic field. The possible process of the magnetic reconnection of the limb flare on Feb. 20-21, 1992 in this active region is proposed also based on the analogy with the flare on Feb. 24-25 near the center of the solar disk. Title: Density Structure of the Coronal Loops Derived from the 1991 Total Eclipse Observation Authors: Takeda, A.; Kurokawa, H.; Kitai, R.; Ishiura, K. Bibcode: 2000ASPC..205..113T Altcode: 2000ltse.conf..113T High-resolution images of the corona obtained during the total solar eclipse on 11th July, 1991 were carefully analyzed to derive the electron densities along the loops of the green(530.3 nm) and red(637.4 nm) emission lines. We found no difference more than a factor of 2 between the averaged densities of the green and the red line loops at corresponding heights. Most of the analyzed loops were found to be approximately in hydrostatic equilibrium. Title: Contribution and Properties of the Green- and Red-Line Coronal Loops in the K-Corona Authors: Takeda, Aki; Kurokawa, Hiroki; Kitai, Reizaburo; Ishiura, Kiyomi Bibcode: 2000PASJ...52..375T Altcode: A set of high-resolution images of corona obtained during the total solar eclipse on 1991 July 11, was carefully analyzed to investigate the properties of the loop structures observed in the green (530.3 nm) and red (637.4 nm) emission lines and in the continuum. With the help of a structure-enhancement algorithm, we have quantitatively shown that: (1) The green- and red-line loops are quite separately distributed in space. (2) For most structures seen in the continuum in the active-region corona, components can be identified in the green or red line. (3) In the innermost corona, structures in the red-line tend to contribute more to the total column density than the green-line structures. We present two schematic models to explain the spatial relation of the green-line, the red-line, and the continuum loops. Next, we studied individual loops in the green and red lines, and derive that their electron densities are almost the same. We also propose a method to determine the `background contribution' of the green and red lines to the total column density derived from the continuum intensity. It is found that the total column density in the analyzed region can be reasonably explained by a mixture of the 530.3 nm component with a line-of-sight length comparable to the size of the active region, and the 637.4 nm component, which tends to concentrate in loop structures. We thereby conclude that the observed corona is well explained by a plasma of temperatures ranging from 2 MK to 1 MK. Title: Emergence of Twisted Magnetic-Flux Bundles and Flare Activity in a Large Active Region, NOAA 4201 Authors: Ishii, Takako T.; Kurokawa, Hiroki; Takeuchi, Tsutomu T. Bibcode: 2000PASJ...52..337I Altcode: To reveal what is the key agent for strong flare activity, we studied the evolution of a large sunspot group, NOAA 4201, and its flare activity. We analyzed high-resolution Hα images obtained with the Domeless Solar Telescope at Hida Observatory, and Kitt Peak full disk magnetograms. We examined the sunspot proper motions and evolutionary changes of Hα fine structures and magnetic fields in this active region, and constructed a schematic model of emerging twisted magnetic-flux bundles. We also found that the occurrence of high flare activity was restricted to the rapidly emerging region of the twisted flux bundle. This fact suggests that the emergence of a twisted emerging flux bundle should be the key to high flare productivity of the sunspot group. Title: Characteristics of Flare-productive Sunspot Groups Authors: Ishii, T. T.; Kurokawa, H.; Takeuchi, T. T. Bibcode: 2000IAUJD...7E..19I Altcode: The mechanism of flare energy build-up is one of the most fundamental questions in the solar flare study, but is still to be solved. >From the review of the previous studies, we notice that the formation process of the magnetic shear in an active region should be essential for the flare energy build-up mechanism. Based on this idea, we make detailed studies of the active region evolutions using high resolution Hα images obtained with the 60 cm Domeless Solar Telescope at Hida Observatory, Kyoto University. We study sunspot proper motions and evolutionary changes of Hα fine structures and magnetic fields in active regions NOAA 5395 and NOAA 4201. To explain the evolutionary characteristics found from the analyses of these two active regions, we propose schematic models of twisted flux bundles emerging from the convection zone. We also found that the occurrence of high flare activity in each active region was restricted to the rapidly emerging region of the twisted flux bundle. In conclusion, we suggest that the emergence of the twisted flux bundle should be the key to high flare-productivity of the sunspot group, or the flare energy build-up mechanism. Title: Relationship Between Hα AFS Loops and Soft X-Ray Brightening Loops in Emerging Flux Regions Authors: Kurokawa, H.; Yoshimura, K. Bibcode: 2000AdSpR..25.1825K Altcode: Close correlations were found between Hα dark emerging loops and soft x-ray loop brightenings from five coordinated observations of emerging flux regions between the Soft X-ray Telescope (SXT) aboard Yohkoh satellite and the Domeless Solar Telescope (DST) of Hida Observatory. The results for the EFR of NOAA 7495 (4-5 May, 1993) are presented in some detail Title: Hα. Surges in Emerging Flux Regions as an Evidence of Magnetic Field Reconnection Authors: Kurokawa, H.; Sano, S. Bibcode: 2000AdSpR..26..441K Altcode: The morphological and dynamical characteristics of a typical EFR-surge, which was observed with a high resolution Hα filtergraph are examined in details. Two kinds of downward-moving features were found in the Hα surge region: One is along the same magnetic field line as that of the upward-moving feature. The other streams along a different magnetic field line where no upward-moving feature was found. It is shown that these two kinds of downward-moving features along the different magnetic field lines are well explained by a magnetic field reconnection between emerging magnetic loops and pre-existing coronal magnetic field Title: Multi-Wavelength Observations of a Large-Scale Jet and an Eruptive- Prominence on 28 August 1992 Authors: Watanabe, Ta.; Ashizawa, K.; Nakagawa, Y.; Miyazaki, H.; Irie, M.; Ichimoto, K.; Kurokawa, H.; Hudson, H.; Yatagai, H. Bibcode: 1999spro.proc..171W Altcode: An eruption of a large (15o) north-south aligned quiescent prominence and associated coronal disturbance, which took place above the eastern solar limb near the equator on 28 August 1992, were observed at a wide range of wavelengths ranging from soft X-rays (Yohkoh) to microwaves (Nobeyama). The eruption was preceded by the formation of a large-scale jet which was apparently ejected near the root of the southern leg of the prominence. The characteristic outward speed of the jet was 450 km s-1. A potential-field presentation of the coronal magnetic field suggests that the jet was formed along the open field which was located immediately to the west of the magnetic arcade, originally surrounding the eruptive prominence. The temperature of the jet is suggested to be comparable to that of the nearby quiet corona (2 × 106 K). In the course of the prominence eruption, helically twisted loops surrounding the prominence were observed. This suggests that magnetic reconnection of the sheared arcade took place underneath the erupting prominence. Title: Causal Relations between Hα Loop Emergences and Soft X-Ray Brightenings Authors: Yoshimura, Keiji; Kurokawa, Hiroki Bibcode: 1999ApJ...517..964Y Altcode: We compared high-resolution images of an emerging flux region in Hα and in soft X-ray, using two types of coalignments. Hα images were taken at Hida Observatory. Soft X-ray images were taken by the Soft X-ray telescope onboard Yohkoh. These data were obtained through coordinated observations by Hida Observatory and Yohkoh. Soft X-ray brightenings were found above most of the emerging Hα arch filaments, which are traces of rising magnetic flux tubes. The released energies in the soft X-ray brightenings were found to be ~1027 ergs, which is consistent with an estimate of energy release through magnetic reconnection between coronal fields and rising flux tubes as an Hα arch filament. These observational results indicate that an arch filament or rising magnetic flux tube itself is not heated up to coronal temperature as soon as it has reached coronal heights, but it can induce a change of magnetic structure through magnetic reconnection in the overlying corona. We also studied the structure of an arch filament in detail at its birth stage. Its morphological feature and evolutionary characteristics can be well explained by the asymmetric rising of a flux tube. Title: An observational search for giant cells in the sun Authors: Kitai, R.; Kurokawa, H.; Funakoshi, Y.; Ishiura, K.; Kimura, G.; Shinkawa, T. Bibcode: 1999AdSpR..24..237K Altcode: With the supergranular network pattern seen in Hα wing image of the Sun as tracers, we derived large-scale horizontal flow field over the solar surface by a local-correlation-tracking method. We have found some evidences of the existence of large scale flow cells on the Sun. Title: Emergence of a Twisted Magnetic Flux Bundle as a Source of Strong Flare Activity Authors: Ishii, Takako T.; Kurokawa, Hiroki; Takeuchi, Tsutomu T. Bibcode: 1998ApJ...499..898I Altcode: 1997astro.ph..8208I Sunspot proper motions and flares of a super active region NOAA 5395--the largest and most flare-active region in the 22d sunspot cycle--were analyzed in detail. We measured sunspot proper motions by using the Hα - 5.0 Å images obtained with the 60 cm Domeless Solar Telescope (DST) at Hida Observatory, Kyoto University and found some peculiar vortex-like motions of small satellite spots, which successively emerged from the leading edge of this sunspot group. To explain these motions of small sunspots, we proposed a schematic model of the successive emergence of twisted and winding magnetic flux loops coiling around a trunk of a magnetic flux tube. The location of the strongest flare activity was found to coincide with the site of the vortex-like motions of sunspots. We conclude that the flare-productive magnetic shear is produced by the emergence of the twisted magnetic flux bundle. Magnetic energy is stored in the twisted flux bundle, which is originally formed in the convection zone and released as flares in the course of the emergence of the twisted flux bundle above the photosphere. Title: An Interdisciplinary Study of the Eruptive Prominence of 28 August 1992 Authors: Watanabe, Ta.; Yamamoto, M.; Hudson, H.; Irie, M.; Ichimoto, K.; Kurokawa, H.; Yatagai, H. Bibcode: 1998ASSL..229..101W Altcode: 1998opaf.conf..101W No abstract at ADS Title: Magnetic Reconnection in the Active Region Inferred by Homologous Soft X-ray Flares in February 1992 Authors: Zhang, H. Q.; Sakurai, T.; Shibata, K.; Shimojo, M.; Kurokawa, H.; Morita, S.; Uchida, Y. Bibcode: 1998ASSL..229..391Z Altcode: 1998opaf.conf..391Z No abstract at ADS Title: Soft X-ray Observations of Eruptive Prominences Authors: Watanabe, T.; Yamamoto, M.; Hudson, H.; Irie, M.; Ichimoto, K.; Kurokawa, H.; Yatagai, H. Bibcode: 1998ASPC..150..376W Altcode: 1998IAUCo.167..376W; 1998npsp.conf..376W No abstract at ADS Title: Coronal and Interplanetary Disturbances Associated with an Eruptive Prominence of 28 August 1992 Authors: Watanabe, T.; Yamamoto, M.; Hudson, H.; Irie, M.; Ichimoto, K.; Kurokawa, H.; Yatagai, H. Bibcode: 1998asct.conf..313W Altcode: No abstract at ADS Title: Comparison between arch filaments and coronal loops. Authors: Yoshimura, K.; Kurokawa, H.; Sano, S.; Hudson, H. Bibcode: 1997IAUJD..19E..60Y Altcode: Kawai et al. (1992) presented preliminary results from comparison between arch filament system (AFS) and soft X-ray (SXR) loops. They found the AFS was covered with the SXR bright features. Coordinated observations with YOHKOH enable us to make more detail comparison between arch filament(AFS) and SXR loops. (With small brightening points both in SXR and H alpha images, we can co-align those images accurately enough.) We intended to see how each AFS contributes to SXR brightenings. We will show examples of AFS which no particular SXR brightening occurred around. And we will present observations of SXR major brightenings of loops, which was related to H alpha dark features. The dark features did not seem to be AFS. They may be small active region filaments which indicates magnetic sheared structure (evidence for storages of extra magnetic energy). Title: Emergence of Twisted Magnetic Flux Tubes Inferred from Sunspot Proper Motions Authors: Ishii, T. T.; Kurokawa, H. Bibcode: 1997IAUJD..19E..25I Altcode: Solar activities are closely related with magnetic field characteristics. Especially, some properties of emerging magnetic fields (e.g. shapes, strength, velocities) concern mechanisms of solar activities. Twists of magnetic flux tubes are thought to store energy for flares and surges. A large active region observed in March 1989, NOAA 5395, was an extremely flare-productive sunspot group with delta-type configuration. We measured proper motions of sunspots in this region by using H alpha images obtained with the 60-cm Domeless Solar Telescope (DST) at Hida Observatory, Kyoto University to construct a schematic model of flux-tube structures in the region. In this study we demonstrate that twisted magnetic flux tubes successively emerged at the leading edge of the great sunspot group and that they played an essential role in the production of strong flare and surge activities of the region. Title: The H alpha filament disappearance on February 20, 1994 Authors: Shinkawa, T.; Koshiishi, H.; Kurokawa, H.; Hanaoka, Y.; Enome, S.; Akioka, M.; Liu, Y. Bibcode: 1997IAUJD..19E..46S Altcode: Solar flares and prominence eruptions are considered as sources of interplanetary and geomagnetic storms. An H alpha filament disappearance and a following big flare whose importance was 3B in H alpha and M4 in GOES X-ray class occurred near the solar disc center on February 20, 1994. This event caused a strong geomagnetic storm. The event was fully observed in H alpha, H alpha+0.8 AA and H alpha-0.8 AA with the Flare Monitoring Telescope at Hida Observatory, Kyoto University, and in 17GHz continuum with the Nobeyama Radio Heliograph. The H alpha, H alpha+0.8 AA and H alpha-0.8 AA images gave us dynamical features of the disappearing filament at the initial stage of the eruption. The 17GHz data revealed much faster motions of the erupting filament across the solar disc and even outside of the solar limb, since it is insensitive to line-of-sight motion. Combining these data, we reconstruct a three-dimensional model of the filament eruption. Title: Casual Relation Between Emerging H alpha AFS Loops and Soft X-ray Transient Brightenings Authors: Kurokawa, H.; Yoshimura, K.; HIDA Dst Team; YOHKOH SXT Team Bibcode: 1997IAUJD..19E..30K Altcode: We study the causal relation between H alpha arch filament system (AFS) loops and corresponding soft X-ray features by using the 60cm Domeless Telescope (DST) of Hida Observatory and the Soft X-ray Telescope aboard Yohkoh. The scientific aims are the followings: (1) Which type of soft X-ray features spatially and temporally correlate to H alpha dark AFS loops? It is important for the study of heating of active region corona. (2) Which type of characteristics and changes in H alpha AFS loops are associated with soft X-ray transient brightenings. It is important for the mechanism of microflare and a trigger of a larger flare. We made coordinated observations between the Hida DST and the Yohkoh SXT four times. Main preliminary results are; (1) A group of H alpha AFS loops generally correlates in space with bright X-ray loops. (2) Some examples showing clear causal relation between a newly emerging H alpha AFS loop and a soft X-ray transient brightening are found. In many cases it is, however, unclear because of lack of resolutions. (3) Newly and actively emerging AFS with sheared structures may cause brighter and frequent X-ray brightenings. We discuss the importance of more feature coordinated observations with higher resolution. Title: Global and Fine Scale Distribution of the Innermost Coronal Temperature Authors: Takeda, A.; Kurokawa, H.; Kitai, R.; Ishiura, K. Bibcode: 1997IAUJD..19E..50T Altcode: The observations of the solar corona at the total eclipses continue to provide us with valuable data, which enables us to study the thermo dynamic structures. Because of the extremely low scattered lights, coronal emission intensities measured during the eclipse time are still higher in accuracy and resolution than the observation from space. It is rare chance to study temperature and density structure of the very innermost part of the corona at visible wavelengths. In this paper, we present the spatial variations of the absolute intensities of the active region corona from 1.05 to 1.5 Rodot observed at the total eclipse of 11th July, 1991, in three wavelengths of 2 coronal emission lines (Fe XIV 530.3 nm and Fe X 637.4 nm) and the continuum around 610.0nm. Global temperature estimation by taking the intensity ratio, Fe XIV/Fe X, indicates that average temperature is not always the highest in the prominent active region corona, since there exists large amount of the cooler plasma together with the hotter component. Next, we examine spatial correlation among the fine structures at above three wavelengths, and show semi-quantitatively that most 1.0 times 10^6K (Fe X) and 2.0 times 10^6K (Fe XIV) plasma are isolated with each other, and that, if they combined, they explain about 70% of the continuum structures. Title: A Filament Eruption and Accompanying Coronal Field Changes on November 5, 1992 Authors: McAllister, A. H.; Kurokawa, H.; Shibata, K.; Nitta, N. Bibcode: 1996SoPh..169..123M Altcode: An Hα filament eruption on November 5, 1992 was fully observed in Hα with the Hida Flare Monitoring Telescope, while Yohkoh's Soft X-ray Telescope observed the pre- and post-eruption evolution of the coronal magnetic fields. From the Hα data, including the red and blue wings, we have reconstructed the rise of the filament, including trajectory, velocity, and acceleration. In combination with the Yohkoh data this reconstruction suggests that the filament had several interactions with other coronal magnetic fields during the eruption. The Yohkoh data also shows pre-eruption changes in the coronal fields and several post-eruption bright coronal structures. The pre-eruption changes are interpreted as a partial opening of the corona, indicating that it is not necessary to have a complete opening of the corona in order for a filament to erupt and we discuss the several possible contributions from emerging flux. The post-event bright coronal structures are compared with theory and with a cleaner filament eruption event on July 31, 1992. These comparisons suggest that, although there are many similarities, it is hard to completely reconcile the observations with the existing theory. Title: The solar origins of two high-latitude interplanetary disturbances Authors: Hudson, H. S.; Acton, L. W.; Alexander, D.; Harvey, K. L.; Kahler, S. W.; Kurokawa, H.; Lemen, J. R. Bibcode: 1996AIPC..382...84H Altcode: Two extremely similar interplanetary forward/reverse shock events, with bidirectional electron streaming, were detected by Ulysses in 1994 [Gosling et al., 1994]. Both events resulted in geomagnetic storms and presumably were associated with coronal mass ejections. In this paper we use the Yohkoh soft X-ray observations to characterize the conditions in the lower corona at the times appropriate for the launching of these two events. We find two strikingly different solar events to be the likeliest candidates: an LDE flare on 20 Feb. 1994, and a extremely large-scale arcade event on 14 April 1994. Title: Chromospheric ejections and their signatures in X-ray observed by YOHKOH Authors: Schmieder, B.; Mein, N.; Shibata, K.; van Driel-Gesztelyi, L.; Kurokawa, H. Bibcode: 1996AdSpR..17d.193S Altcode: 1996AdSpR..17..193S Surges, or condensations of chromospheric material, are commonly observed in active regions when new emerging magnetic flux (EMF) occurs. In order to study EMF-related phenomena in the corona, observing campaigns were organized with the Yohkoh X-ray satellite and ground based observatories. EMFs could be detected in magnetograms made in Potsdam and Hawaii, surge and arch filament system (AFS) events (on Oct 7 1991, May 1 1993, respectively) with the Multichannel Subtractive Double Pass instruments operating at Meudon and on the Canary Islands and with the Hida telescope at Kyoto University. Bright X-ray loops coincident with chromospheric surge activity were detected in the high resolution Yohkoh SXT images. We also found coincident brightness variations between an X-ray bright point (XBP) and the underlying chromospheric plage related to EMF. We interpret the appearance of AFS as condensation of material among magnetic field lines, the X-ray bright points as the result of a magnetic reconnection process, and surges as ejection of cold plasma bubbles squeezed between field lines as a result of reconnection. Title: X-Ray Bright Point Flares Due to Magnetic Reconnection Authors: Van Driel-Gesztelyi, L.; Schmieder, B.; Cauzzi, G.; Mein, N.; Hofmann, A.; Nitta, N.; Kurokawa, H.; Mein, P.; Staiger, J. Bibcode: 1996SoPh..163..145V Altcode: Ground-based optical observations coordinated with Yohkoh/SXT X-ray observations of an old, disintegrating bipolar active region AR NOAA 7493 (May 1, 1993) provided a multiwavelength data base to study a flaring `active region' X-ray bright point (XBP) of about 16 hr lifetime, and the activity related to it in different layers of the solar atmosphere. The XBP appeared to be related to a new minor bipole of about 1020 Mx. Superposed on a global evolution of soft X-ray brightness, the XBP displayed changes of brightness, lasting for 1-10 min. During the brightenings the XBP apparently had a spatial structure, which was (tiny) loop-like rather than point-like. The X-ray brightenings were correlated with chromospheric activity: (i) brightenings of underlying chromospheric faculae, and (ii) appearance of strong turbulent velocities in the arch filament system. We propose that the XBP brightenings were due to reconnection of the magnetic field lines (sketched in 3D) between the new bipole and a pre-existing plage field induced by the motion of one of the new pores (v = 0.2 km s−1) towards the plage, and that the XBP itself was a reconnected hot loop between them. Title: Causal Relation between H alpha Arch Filament Loops and Soft X-ray Coronal Loops Authors: Yoshimura, K.; Kurokawa, H.; Sano, S.; Hudson, H. Bibcode: 1996mpsa.conf..457Y Altcode: 1996IAUCo.153..457Y No abstract at ADS Title: Energy Build-up Processes of Solar Flares Studied by Optical Observations Authors: Kurokawa, H. Bibcode: 1996mpsa.conf..185K Altcode: 1996IAUCo.153..185K No abstract at ADS Title: Comparison of High Resolution Optical and Soft X-ray Images of Solar Corona Authors: Takeda, A.; Kurokawa, H.; Kitai, R.; Ishiura, K.; Golub, L. Bibcode: 1996mpsa.conf..483T Altcode: 1996IAUCo.153..483T No abstract at ADS Title: Emerging Flux, Reconnection, and XBP Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Demoulin, P.; Mandrini, C.; Cauzzi, G.; Hofmann, A.; Nitta, N.; Kurokawa, H.; Mein, N.; Mein, P. Bibcode: 1996mpsa.conf..459V Altcode: 1996IAUCo.153..459V No abstract at ADS Title: Emerging flux seen by Yohkoh. Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Mandrini, C.; Démoulin, P.; Cauzzi, G.; Hofmann, A.; Nitta, N.; Kurokawa, H.; Mein, N.; Mein, P. Bibcode: 1996joso.proc..124V Altcode: No abstract at ADS Title: The solar origins of two high-latitude interplanetary disturbances Authors: Hudson, H. S.; Acton, L. W.; Alexander, D.; Harvey, K. L.; Kurokawa, H.; Kahler, S.; Lemen, J. R. Bibcode: 1995sowi.confS..58H Altcode: Two extremely similar interplanetary forward/reverse shock events, with bidirectional electron streaming were detected by Ulysses in 1994. Ground-based and Yohkoh/SXT observations show two strikingly different solar events that could be associated with them: an LDE flare on 20 Feb. 1994, and a extremely large-scale eruptive event on 14 April 1994. Both events resulted in geomagnetic storms and presumably were associated with coronal mass ejections. The sharply contrasting nature of these solar events argues against an energetic causal relationship between them and the bidirectional streaming events observed by Ulysses during its S polar passage. We suggest instead that for each pair of events. a common solar trigger may have caused independent instabilities leading to the solar and interplanetary phenomena. Title: Evolutional Characteristics of Multiple Spectral Lines during the Impulsive Phase of Solar Flares Authors: Shoji, Makiko; Kurokawa, Hiroki Bibcode: 1995PASJ...47..239S Altcode: A study of the impulsive phase spectra of two chromospheric flares, for which the Hα , CaII K, HeI D_3, NaI D_{1,2} and other metallic lines were simultaneously obtained with high temporal and spatial resolutions, is presented. The main new observational results are: (1) The red-shifted emission streaks observed in the Hα , K, and D_3\ lines give nearly the same downward velocities, the maximum of which ranges from 50 to 100 km s(-1) for typical streaks. (2) The broad Hα , K, and D_3\ line profiles are well explained by a Doppler broadening of nearly the same turbulent velocity, the maximum of which ranges between 120 and 170 km s(-1) . (3) D_{1,2}\ and metallic line emissions show narrow and slightly red-shifted profiles. Their typical maximum downward and turbulent velocities are 2--6 km s(-1) \ and 10 km s(-1) , respectively. (4) K-line emission profiles of the flares consist of two components, i.e., a red-shifted broad wing and a stationary narrow core. (5) All of the emission lines show nearly parallel time-profiles of both the intensity and downward velocity. From these results we conclude that the emitting region of the chromospheric flare consists of two layers heated simultaneously: one relatively thin, fast-downward-moving and very turbulent, and the other almost stationary and optically thick in metallic-line emissions. Title: Peculiar magnetic field evolution of active region NOAA 7562 in August 1993 - results from campaign observation with Yohkoh Authors: Sakurai, T.; Suematsu, Y.; Ichimoto, K.; Kurokawa, H.; Kitai, R.; Akioka, M.; Tohmura, I.; Soltau, D.; Mickey, D. L.; Zhang, H.; Li, W.; Zirin, H.; Tang, F. Bibcode: 1994ESASP.373..337S Altcode: 1994soho....3..337S No abstract at ADS Title: Yohkoh observations of the creation of high-temperature plasma in the flare of 16 December 1991 Authors: Culhane, J. L.; Phillips, A. T.; Inda-Koide, M.; Kosugi, T.; Fludra, A.; Kurokawa, H.; Makishima, K.; Pike, C. D.; Sakao, T.; Sakurai, T.; Doschek, G. A.; Bentley, R. D. Bibcode: 1994SoPh..153..307C Altcode: Yohkoh observations of an impulsive solar flare which occurred on 16 December, 1991 are presented. This flare was a GOES M2.7 class event with a simple morphology indicative of a single flaring loop. X-ray images were taken with the Hard X-ray Telescope (HXT) and soft X-ray spectra were obtained with the Bragg Crystal Spectrometer (BCS) on board the satellite. The spectrometer observations were made at high sensivity from the earliest stages of the flare, are continued throughout the rise and decay phases, and indicate extremely strong blueshifts, which account for the majority of emission in CaXIX during the initial phase of the flare. The data are compared with observations from other space and ground-based instruments. A balance calculation is performed which indicates that the energy contained in non-thermal electrons is sufficient to explain the high temperature plasma which fills the loop. The cooling of this plasma by thermal conduction is independently verified in a manner which indicates that the loop filling factor is close to 100%. The production of `superhot' plasma in impulsive events is shown to differ in detail from the morphology and mechanisms appropriate for more gradual events. Title: Red Asymmetries of Optical Lines at the Impulsive Phase of Solar Flares Authors: Shoji, M.; Kurokawa, H. Bibcode: 1994kofu.symp..409S Altcode: Impulsive phase spectra of two chromospheric flares were obtained with high temporal resolution. H_alpha, Ca II K, He I D_3, and other metallic lines were observed simultaneously and their red asymmetries were studied. Velocities derived from K and D_3 line emissions are found to be as large as H_alpha velocity, contrary to the previous works. Title: A Morphological Study of Magnetic Shear Development in a Flare-Productive Region NOAA 7270 Authors: Kurokawa, H.; Kitai, R.; Kawai, G.; Shibata, K.; Yaji, K.; Ichimoto, K.; Nitta, N.; Zhang, H. Bibcode: 1994kofu.symp..283K Altcode: The evolutional changes of a flare-productive region NOAA 7270 were examined in details with high resolution H_alpha images, magnetograms and soft X-ray images to study the process of the magnetic shear development and its relation to the strong flare activity of the region. This study led us to the following results and a conclusion:(1) Several new bipolar pairs simultaneously and or successively emerged in NOAA 7270 from 5 through 7 September. (2) Magnetic shear configurations developed at three locations, where most of flares occurred from 5 through 7 , September. (3)These magnetic shear configurations were formed by successive emergences of twisted magnetic ropes from below the photosphere. Title: Thermal and Density Structure of the Inner Corona Observed at the 1991 Total Solar Eclipse Authors: Takeda, A.; Kurokawa, H.; Kitai, R.; Ishiura, K. Bibcode: 1994kofu.symp..381T Altcode: We observed the total solar eclipse on 11 July, 1991 with the multi-channel telescope at Lapaz,Mexico, and successfully obtained high-resolution pictures of the innermost corona at the wavelength shown in Table 1. This is a brief summary of preliminary results obtained from the photometric mesurement of the photographic pictures and their image processing. Title: Flares on September 6, 1992 Authors: Kitai, R.; Kurokawa, H.; Funakoshi, Y.; Nakai, Y.; Shibata, K.; Yaji, K.; Nitta, N.; YOHKOH Team; NAOJ Flare Telescope Team Bibcode: 1994kofu.symp..147K Altcode: We present some preliminary results of our observational study of typical eruptive flares in NOAA7270 on September 6, 1992. (1)Magnetic shear and flux emergence are strongly related to flare production. (2)Observed flares showed a common temporal relation between cool plasma dynamics seen in H_alpha and coronal energy releases seen in YOHKOH data. (3)At the pre-heating stage of flares, there were some indications of slow reconnection of adjacent magnetic loops. Title: Simultaneous Observations of a Prominence Eruption Followed by a Coronal Arcade Formation in Radio, Soft X-Rays, and Hα Authors: Hanaoka, Yoichiro; Kurokawa, Hiroki; Enome, Shinzo; Nakajima, Hiroshi; Shibasaki, Kiyoto; Nishio, Masanori; Takano, Toshiaki; Torii, Chikayoshi; Sekiguchi, Hideaki; Kawashima, Susumu; Bushimata, Takeshi; Shinohara, Noriyuki; Irimajiri, Yoshihisa; Koshiishi, Hideki; Shiomi, Yasuhiko; Nakai, Yoshihiro; Funakoshi, Yasuhiro; Kitai, Reizaburo; Ishiura, Kiyomi; Kimura, Goro Bibcode: 1994PASJ...46..205H Altcode: A prominence eruption followed by a coronal brightening was simultaneously observed in radio (17 GHz), soft X-rays, and Hα on 1992 July 30--31. The observations were performed by newly developed high-performance instruments: the Nobeyama Radioheliograph, the SXT on the Yohkoh satellite, the Flare Monitoring Telescope of the Hida Observatory, and some other Hα telescopes. This event gives us a much more detailed picture of this type of phenomena than previously observed. The erupting prominence, which occurred in a quiet region and was observed in Hα and radio, ascended with a velocity of about 100 km s(-1) . The general structure of the erupting prominence seen at 17 GHz is very similar to that at Hα . While the prominence expanded rapidly, the total radio flux of the erupting prominence did not change very much. Since a prominence consists of fine threads, this fact means that each thread did not expand while the prominence expanded. Consequently, the surface filling factor of the prominence must have decreased during the eruption. The high-resolution pictures of a clear coronal arcade structure were taken in soft X-rays and radio after the prominence eruption; the physical parameters of the arcade were derived from these pictures. The mean temperature was 3.5*E(6) K in the early phase, and decreased to 2.6*E(6) K within seven hours. The total emission measure reached a maximum value of 1.6*E(48) cm(-3) after three hours from the beginning of the arcade brightening, when the electron density at the ridge of the arcade is estimated as 2.4*E(9) cm(-3) . The temporal and spatial relationship between the erupting prominence and the coronal arcade is shown. It gives an observational restriction to the magnetic field configuration of the models of such events. Title: Attempt to Observe the Sodium Exosphere of Mercury During the 1993 Solar Transit Authors: Potter, A. E.; Talent, D.; Kurokawa, H.; Kawakami, S.; Morgan, T. H. Bibcode: 1994LPI....25.1099P Altcode: No abstract at ADS Title: High-Resolution Spectral Observation during the Impulsive Phase of a Flare Authors: Ji, G. P.; Kurokawa, H.; Fang, C.; Huang, Y. R. Bibcode: 1994SoPh..149..195J Altcode: High-resolution observations of the flare on October 21, 1989 were made with the Domeless Solar Telescope of the Hida Observatory. The following new results have been obtained: (a) during the impulsive phase of the flare, the spectral line asymmetry has spatial fine structures of 1″-2″; (b) for several points in the flare region the line profile alternatively changes between blue asymmetry and red asymmetry within a few seconds. A possible explanation has been suggested. Title: Fine Structures of the Inner Corona Observed at the 1991 Total Solar Eclipse Authors: Takeda, A.; Kurokawa, H.; Kitai, R.; Ishiura, K. Bibcode: 1994scs..conf..565T Altcode: 1994IAUCo.144..565T No abstract at ADS Title: Filament Tether Cutting Before a Major Eruptive Flare Authors: Canfield, R. C.; Blais, K. A.; Reardon, K. P.; Acton, Loren; Kurokawa, H. Bibcode: 1994ASPC...68..411C Altcode: 1994sare.conf..411C No abstract at ADS Title: The X Flare of 15 November, 1991: Preflare Flux Emergence, Heating and Filament Eruption Authors: Canfield, R. C.; Blais, K. A.; McClymont, A. N.; Metcalf, T. R.; Reardon, K. P.; Wülser, J. -P.; Acton, L. W.; Kurokawa, H.; Hirayama, T. Bibcode: 1994xspy.conf..153C Altcode: No abstract at ADS Title: Transient Brightenings of Soft X-Ray Loops in Emerging Flux Regions Authors: Kurokawa, H.; Kawai, G.; Tsuneta, S.; Ogawara, Y. Bibcode: 1994xspy.conf...59K Altcode: No abstract at ADS Title: Diagnostics of Twisted Flux Emergence (noaa AR7260) Authors: Leka, K. D.; van Driel-Gesztelyi, L.; Anwar, B.; Canfield, R. C.; Hudson, H. S.; Metcalf, T. R.; Mickey, D. L.; Nitta, N.; Kurokawa, H. Bibcode: 1994xspy.conf...25L Altcode: No abstract at ADS Title: A Prominenece Eruption Followed by a Coronal Arcade Formation on July 30-31, 1992 Authors: Hanaoka, Y.; Kurokawa, H.; Enome, S.; Nakajima, H.; Shibasaki, K.; Nishio, M.; Takano, T.; Torii, C.; Sekiguchi, H.; Kawashima, S.; Bushimata, T.; Shinohara, N.; Irimajiri, Y.; Koshiishi, H.; Shiomi, Y.; Nakai, Y.; Funakoshi, Y.; Kitai, R.; Ishiura, K.; Kimura, G. Bibcode: 1994xspy.conf..193H Altcode: No abstract at ADS Title: Prominence Eruption in NOAA7125 on April 6, 1992 Authors: Kitai, R.; Kawai, G.; Anwar, B.; Kurokawa, H.; Funakoshi, Y.; Nakai, Y.; Tsuneta, S. Bibcode: 1994xspy.conf..287K Altcode: No abstract at ADS Title: Filament Tether Cutting Before a Major Eruptive Flare Authors: Canfield, R. C.; Blais, K. A.; McClymont, A. N.; Metcalf, T. R.; Reardon, K. P.; Wuelser, J. -P.; Acton, L. W.; Kurokawa, H. Bibcode: 1993BAAS...25.1188C Altcode: No abstract at ADS Title: Flares on 1992 September 6 Authors: Shibata, K.; Nitta, N.; Kitai, R.; Kurokawa, H.; Yaji, K.; Kato, T.; Zarro, D. M. Bibcode: 1993BAAS...25R1187S Altcode: No abstract at ADS Title: H alpha Surge Activity at the First Stage of Magnetic Flux Emergence Authors: Kurokawa, H.; Kawai, G. Bibcode: 1993ASPC...46..507K Altcode: 1993IAUCo.141..507K; 1993mvfs.conf..507K No abstract at ADS Title: Comparison between YOHKOH Soft X-ray Images and 3D MHD Simulations of Solar Emerging Flux Regions Authors: Matsumoto, R.; Tajima, T.; Kaisig, M.; Shibata, K.; Ishido, Y.; Tsuneta, S.; Shimizu, T.; Kawai, G.; Kurokawa, H.; Akioka, M.; Acton, L.; Strong, K.; Nitta, N. Bibcode: 1992AAS...181.8109M Altcode: 1992BAAS...24.1253M The soft X-ray telescope on the Yohkoh mission enabled us to observe the evolution of emerging flux regions (EFR) in coronal X-rays with high spatial and temporal resolution. Furthermore, we now have enough computing capability to perform three-dimensional MHD simulation of EFRs with sufficient spacial resolution to study details of the flux emergence process. These new tools provide the opportunity to investigate the physics involved in the formation of coronal loops in much more detail. We carried out 3D MHD simulations of emerging magnetic flux regions under various intial conditions; (1) a horizontal magnetic flux sheet, (2) a bundle of horizontal flux tubes, and (3) a flux sheet with sheared magnetic fields. Numerical results show that coronal magnetic loops are formed due to the enhanced buoyancy resulting from gas precipitating along magnetic field lines. The interchange modes help to produce a fine fibrous structure perpendicular to the magnetic field direction in the linear stage, while the undular modes determine the overall loop structure. We observe in 3D simulations that during the ascendance of loops the bundle of flux tubes, or even the flux sheet, developes into dense filaments pinched between magnetic loops. We also find that magnetic field lines are twisted by the vortex motion produced by the horizontal expansion of magnetic loops. Our numerical results may explain the observed signatures such as (1) the spacial relation between soft X-ray loops and Hα arch filaments obtained by coordinated observation between Yohkoh and ground-based observatories (Kawai et al. 1992), (2) the rate of increase in size of soft X-ray loops in EFRs (Ishido et al. 1992), (3) emergence of twisted magnetic loops, and (4) the threshold flux for formation of chromospheric arch filament systems (AFS). Title: Detailed Comparison between Hα and YOHKOH Soft X-Ray Images of a Confined Two-Ribbon Flare Authors: Kurokawa, Hiroki; Kawai, Goro; Kitai, Reizaburo; Funakoshi, Yasuhiro; Nakai, Yoshihiro; Tsuneta, Saku; Kosugi, Takeo; Enome, Shinzo; Acton, Loren W.; Ogawara, Yoshiaki Bibcode: 1992PASJ...44L.129K Altcode: The spatial and temporal relationships between soft X-ray loops and Hα flare Kernels were studied for the 1B (M2.6) flare of 1991 December 5. Most of flare energy was released inside three soft X-ray loops whose footpoints were bright as Hα Kernels. We suggest that the interaction among pre-existing or emerging magnetic loops is essential for the successive energy release in a confined two-ribbon flare. Title: Comparison between Hα and YOHKOH Soft X-Ray Images of Emerging Flux Regions Authors: Kawai, Goro; Kurokawa, Hiroki; Tsuneta, Saku; Shimizu, Toshifumi; Shibata, Kazunari; Acton, Loren W.; Strong, Keith T.; Nitta, Nariaki Bibcode: 1992PASJ...44L.193K Altcode: We carried out a detailed comparison between Hα and Yohkoh Soft X-ray (SXR) images of three emerging flux regions. The main results are: (1) In general, SXR bright features coincide well in space with Hα arch filament systems in the emerging flux regions (EFR). (2) Some young and active parts of EFRs are especially bright in SXR. (3) The SXR structures related to EFR show fairly rapid changes in both brightness and shape. These results are consistent with the model that the emerging cool loops of EFRs evolve into hot coronal loops through some heating processes. Title: Fine Structures of Chromospheric Magnetic Field and Material Flow in a Solar Active Region Authors: Zhang, Hongqi; Ai, Guoxiang; Sakurai, T.; Kurokawa, H. Bibcode: 1991SoPh..136..269Z Altcode: In this paper, we analyze the relations between photospheric vector magnetic fields, chromospheric longitudinal magnetic fields and velocity fields in a solar active region. Agreements between the photospheric and chromospheric magnetograms can be found in large-scale structures or in the stronger magnetic structures, but differences also can be found in the fine structures or in other places, which reflect the variation of the magnetic force lines from the photosphere to the chromosphere. The chromospheric superpenumbral magnetic field, measured by the Hβline, presents a spoke-like structure. It consists of thick magnetic fibrils which are different from photospheric penumbral magnetic fibrils. The outer superpenumbral magnetic field is almost horizontal. The direction of the chromospheric magnetic fibrils is generally parallel to the transverse components of the photospheric vector magnetic fields. The chromospheric material flow is coupled with the magnetic field structure. The structures of the Hβ chromospheric magnetic fibrils in the network are similar to Hβ dark fibrils, and the feet of the magnetic fibrils are located at the photospheric magnetic elements. Title: Optical Observations of Flare-Productive Flux Emergence Authors: Kurokawa, H. Bibcode: 1991LNP...387...39K Altcode: 1991LNP...387...37K; 1991fpsa.conf...39K The optical observations of the relationship between emerging magnetic fluxes and flares are reviewed and the characteristics essential to the flare-productive emerging flux regions are studied. Examining several essential parameters, i.e. location of emergence, orientation of bipolar axis, growth rate and magnetic shear development, we conclude that the emergence of twisted magnetic flux ropes is the most important factor for the major flare activities. Some observational evidence of the emergence of the twisted magnetic flux ropes is demonstrated with high resolution H pictures. Title: High resolution observations of active phenomena obtained at Hida Observatory Authors: Kurokawa, H.; Nakai, Y.; Funakoshi, Y.; Kitai, R. Bibcode: 1991AdSpR..11e.233K Altcode: 1991AdSpR..11..233K Samples of high-resolution observations of solar active regions and flares obtained with the 60-cm Domeless Solar Telescope (DST) at Hida Observatory, Kyoto University are presented. What gives rise to the twist and shear in the magnetic loop structures is the essential question for the study of solar active phenomena. Several examples showing the development of twisted or sheared magnetic structures are demonstrated and morphologically studied. Two examples of high-resolution spectra of a flare and spicules are also demonstrated. Title: High-Resolution Observation and Detailed Photometry of a Great Hα Two-Ribbon Flare Authors: Kitahara, T.; Kurokawa, H. Bibcode: 1990SoPh..125..321K Altcode: A great Hα two-ribbon flare of 12 October, 1981 was observed with the Domeless Solar Telescope at the Hida Observatory and its detailed photometry was made with a two dimensional microdensitometer. The principal results are as follows: (1) The impulsive phase of the flare started with the progressive brightenings of flare points forming the front lines of the Hα two ribbons at both sides of the magnetic neutral line. These are followed by the explosive expansion of Hα two ribbons at the main impulsive phase. (2) Three typical shapes of Hα light curves were found. The type 1 light curve is characterized by the primary impulsive rise and rapid fall of intensity. The light curve of type 3 has no impulsive component but has a very gradual maximum. The type 2 profile attains the main gradual maximum with a few small impulsive peaks. These different types of light curves are made by different heating mechanisms, those are electron precipitation, heat conduction and soft X-ray radiation respectively. (3) The light curve of total intensity, which was made by integrating Hα - 1.0 Å intensities of the whole main Hα flare region, shows a primary impulsive peak and a later gradual maximum. The former peak coincides in time with that of the hard X-ray emission. The latter maximum is well correlated with the soft X-ray maximum. (4) The brightest flare points with time profiles of type 1 are closely related to the impulsive hard X-ray emissions of highest energy. Title: High-Resolution Observations of Hα Flare Regions Authors: Kurokawa, Hiroki Bibcode: 1989SSRv...51...49K Altcode: This paper gives a review of the recent high-resolution Hα observations of solar flares and flare-productive active regions. From studies of the morphological and evolutional features of Hα flare emitting regions, two types of two-ribbon flares, which are termed separating two-ribbon flare and confined two-ribbon flare, are discussed. The former is characterized by conspicuous separating motions or expanding motions of the Hα two ribbons, whereas the latter shows only a short range of or no separating motions of the two ribbons. The explosive compact flares, which occur in some compact newly-emerging flux regions, are also discussed. Attention is paid to the successive and impulsive brightenings of Hα flare points which form the Hα flare kernels and the front lines of Hα two ribbons at the impulsive phases of flares. Temporal relationships between Hα line intensities or profiles and hard X-ray or microwave emissions are discussed to discriminate the energy transport mechanisms in the flare loops. Hα monochromatic image of high spatial resolution, at the present time, is the most sensitive detector for finding the first appearance of newly-emerging magnetic flux region and the developing features of sheared configuration of magnetic field, both of which are the key factors in flare energy build-up processes. It is suggested that the successive emergence of a twisted magnetic flux rope might be essential for the production of a major flare. Title: Mass Motions in Active Region Filaments Authors: Hanaoka, Yoichiro; Kurokawa, Hiroki Bibcode: 1989SoPh..124..227H Altcode: Mass motions in active region filaments of regions NOAA 4171 and McMath 16208 are analyzed. Both regions were continuously observed with the Zeiss Lyot filter for about a week at the Hida Observatory. As for NOAA 4171, Dopplergrams are made from the Hα filtergrams of 7 wavelengths for the qualitative study of the velocity fields in the filament, and Beckers' cloud model analysis is employed for a quantitative study of them. Dopplergrams of McMath 16208 are also constructed for qualitative analyses to determine whether the results derived from the analysis of NOAA 4171 are applicable to this region. Title: Detailed comparison of transverse magnetic fields of the sun with H-alpha fine structures Authors: Kawakami, Singo; Makita, Mitsugu; Kurokawa, Hiroki Bibcode: 1989PASJ...41..175K Altcode: Vectormagnetograms obtained at the Okayama Astrophysical Observatory are compared in detail with H-alpha filtergrams taken with the Domeless Solar Telescope at Hida Observatory for three active regions. The coincidence rate between the azimuth of transverse magnetic fields and elongated H-alpha dark fine structures decreases as the active region moves on the solar disk from the center to the limb. This center-to-limb variation of the azimuthal coincidence rate can be explained by the difference of elevation angle between the photospheric and chromospheric magnetic fields. The analysis of three active regions shows that, in a more active region, the magnetic field is more inclined in the photosphere, and more sheared in the vertical direction. Three active regions show different values of the azimuthal coincidence rate, and these differences are discussed in connection with the magnetic field configuration and the evolutional characteristics of the individual active regions. Title: Plasma Motions in an Emerging Flux Region Authors: Brueckner, G. E.; Bartoe, J. -D. F.; Cook, J. W.; Dere, K. P.; Socker, D.; Kurokawa, H.; McCabe, M. Bibcode: 1988ApJ...335..986B Altcode: Ultraviolet spectra of C IV show large nonthermal broadening in an area of emerging flux. These nonthermal motions are observed at a very early stage of reconnecting field lines. The spectra can be traced to small, rapidly changing surge or filament-like features which are seen in the center, blue, and red wing of H-alpha. They seem to have the characteristics of macrospicules or explosive events. They are precursors of the reconnection process. Plasma turbulence and/or plasma waves in the reconnecting plasma may cause the broad C IV line profiles. The activity in the transition zone precedes the formation of a bright chromospheric loop system. Title: A coronal condensation observed at the total solar eclipse of June 11, 1983 and a related transient prominence Authors: Suematsu, Yoshinori; Saito, Sumisaburo; Funakoshi, Yasuhiro; Kurokawa, Hiroki Bibcode: 1988SoPh..116..285S Altcode: A coronal condensation was observed simultaneously with Fexiv λ5303, Fex λ6374, Fe XI λ7892, and Hα filtergraphs. The size and shape of the condensation in λ5303 are different from those in other filtergrams. Hα filtergrams taken around the eclipse time show that a small transient prominence exists in close proximity to the condensation core and behaves like a post-flare loop system, though the appearance is quite different and no flare-report exists. A small-scale energetic phenomenon seems to have occurred at the top of magnetic loops. Title: Active region coronal loops observed at the total solar eclipse of February 16, 1980 Authors: Hanaoka, Yoishiro; Kurokawa, Hiroki; Saito, Sumisaburo Bibcode: 1988PASJ...40..369H Altcode: Coronal loop structures above an active region observed at the total eclipse of February 16, 1980 in Kenya are analyzed. Temperatures and densities of the loops are derived from three monochromatic images of Fe X λ6374 (1×106K or cool corona), Fe XIV λ5303 (2×106K or hot corona), and continuum. These monochromatic images are processed for the analyses, and pure images of the active region corona are obtained. Results from a morphological diagnostics are presented. Title: Close relationship between H-alpha and hard X-ray emissions at the impulsive phase of a solar flare Authors: Kurokawa, Hiroki; Takakura, Tatsuo; Ohki, Kenichiro Bibcode: 1988PASJ...40..357K Altcode: High-resolution Hα images of the March 23, 1982 flare were obtained with the 60-cm Domeless Solar Telescope at the Hida Observatory. The mean temporal resolution of Hα - 1.0-Å images was about 1 s at the impulsive phase of the flare and better than those of any other observations which had been published. This enabled the authors to study the close correlation between Hα light curves and hard X-ray time profiles obtained by the Japanese satellite Hinotori. Main observational results are presented and discussed. Title: Surge activity in an emerging magnetic region of the sun Authors: Kurokawa, H. Bibcode: 1988VA.....31...67K Altcode: From the morphological study of the earliest phase of an emerging flux region, we found that the first manifestation of the emerging flux region on the solar surface is a surge activity. Examining the magnetic field configuration of the surge region, we suggest that the surges in emerging flux regions are produced by the reconnection between newly-emerging fields and older surrounding magnetic fields. Title: Rotating eruption of an untwisting filament triggered by the 3B flare of 25 April, 1984 Authors: Kurokawa, Hiroki; Hanaoka, Yoichiro; Shibata, Kazunari; Uchida, Yutaka Bibcode: 1987SoPh..108..251K Altcode: A great 3B flare, whose X-ray class was X13, occurred over a delta-sunspot at 00: 01 UT on April 25, 1984. Before the flare, a strong magnetic shear was found to be formed along the neutral line in the delta-sunspot with shear motions of umbrae. The shear motions of the umbrae were caused by the successive emergence of a magnetic flux rope. Title: Vapor compression distiller and membrane technology for water revitalization Authors: Ashida, A.; Mitani, K.; Ebara, K.; Kurokawa, H.; Sawada, I.; Kashiwagi, H.; Tsuji, T.; Hayashi, S.; Otsubo, K.; Nitta, K. Bibcode: 1987AdSpR...7d..73A Altcode: 1987AdSpR...7...73A Water revitalization for a space station can consist of membrane filtration processes and a distillation process. Water recycling equipment using membrane filtration processes was manufactured for ground testing. It was assembled using commercially available components. Two systems for the distillation are studied; one is an absorption type thermopervaporation cell and the other is a vapor compression distiller. Absorption type thermopervaporation able to easily produce condensed water under zero gravity was investigated experimentally and through simulated calculation. The vapor compression distiller was studied experimentally and it offers significant energy savings for evaporation of water. Title: Two distinct morphological types of magnetic shear development and their relation to flares Authors: Kurokawa, H. Bibcode: 1987SoPh..113..259K Altcode: 1982SoPh..113..259K From a morphological study of the evolution of six active regions, we found two types of processes for the development of magnetic shear configurations between sunspots: (A) collision of two sunspots of opposite magnetic polarities, and (B) successive emergence of twisted magnetic flux ropes. We conclude that the process (B) might be essential for the production of major flares. Title: The innermost corona observed at the 1973 June 30 eclipse Authors: Hanaoka, Yoichiro; Kanno, Mitsuo; Kurokawa, Hiroki; Tsubaki, Tokio Bibcode: 1986SoPh..106...95H Altcode: Slitless flash spectrograms in heights below 8000 km above the solar limb were obtained by the University of Kyoto Expedition at Atar, Mauritania. The integrated intensities of FeXIVλ5303, FeXλ6374, FeXIλ7892, and the continuum are measured as a function of height above the solar limb at eleven points (P.A. = 284-300°) around the third contact point. It is found that a significant amount of the emission in FeXλ6374 originates in chromospheric levels well below 8000 km. This implies that the interspicular region of the chromosphere is occupied by coronal material. The average values of the electron temperature and the electron density in the interspicular region are derived from the FeXλ6374 and the FeXIλ7892 intensities on the assumption of spherical symmetry: Te = 0.9-1.1 × 106 K and Ne = 9-10 × 108 cm−3. The intensity variations of the coronal lines and the continuum with position angle are also studied. Strong correlations between FeXIVλ5303 and the continuum and between FeXλ6374 and FeXIλ7892 are found. From the FeXλ6374 intensities it is inferred that there is a density fluctuation in the innermost corona by at least a factor of two. Title: The post flare loops observed at the total eclipse of February 16, 1980 Authors: Hanaoka, Y.; Kurokawa, H.; Saito, S. Bibcode: 1986SoPh..105..133H Altcode: A post flare loop system was observed on the west limb at the total solar eclipse of February 16, 1980 in Kenya. Analyzing the monochromatic images and the flash spectra, we obtained the following results: (1) the lower part of the post flare loop system is characterized mainly by distinct cool loops of Hα and Fe x 6374. Fe x 6374 emitting plasma (Te = 1.0 × 106 K) is highly concentrated in the loops. The 6374 loops are broader in diameter and located very close to but a little higher than the corresponding Hα loops. The electron densities of the dense part in Hα and Fe x 6374 loops are 1011 cm-3 and 6 × 109cm-3, respectively; (2) the Ca xv emitting region (3.5 × 106 K) is confined to the upper part of the post flare loops. The electron density of this hot region is estimated as 8 × 109 cm-3 from the Ca xv line intensity ratio, I(λ5694)I(λ5445). These observational results led us to construct an empirical model of the post flare loop system which is consistent with the reconnection model of Kopp and Pneuman (1976). Title: Observations of chromospheric flare dynamics at the next solar maximum specific recommendations of the Chromospheric Flare Dynamics Group. Authors: Canfield, R. C.; Gaizauskas, V.; Kurokawa, H.; Martin, S. F.; Svestka, Z. Bibcode: 1986lasf.conf..489C Altcode: No abstract at ADS Title: High resolution observation of Hα solar flares and temporal relation between Hα and X-ray, microwave emission Authors: Kurokawa, H.; Kitahara, T.; Nakai, Y.; Funakoshi, Y.; Ichimoto, K. Bibcode: 1986Ap&SS.118..149K Altcode: We studied the evolutional characteristics of fine structures in Hα flare emitting regions and their relation to X-ray and microwave emissions for selected events observed with the 60 cm Domeless Solar Telescope at Hida Observatory, University of Kyoto. The principal conclusions of this investigation are: (1) Hα kernel consists of some finer bright points or Hαflare points whose individual size is less than 1 arc sec. (2) Impulsive brightnenings of Hα flare points occurred simultaneously with the spikes of the hard X-ray and microwave bursts within the time resolution of our Hα observations which varied from 1 to 10 s. (3) It is concluded that fast electron beams must be the principal mechanism of heating Hα flares during the impulsive phase of a flare. Title: Impulsive brightening of Hα flare points. Authors: Kurokawa, Hiroki Bibcode: 1986lasf.conf...51K Altcode: 1986lasf.symp...51K The authors showed clearly that flare points are elementary structures of Hα flare emitting regions. Many flare points successively brighten in the chromosphere to form Hα kernels or the front lines of Hα flare ribbons at the impulsive phases of flares. The flare points correspond to the chromospheric footpoints of flare loops and their individual size is less than 1arcsec. Impulsive brightenings of flare points closely synchronize with the hard X-ray or microwave spikes at the early impulsive phases of flares. Title: Periodic behaviour of solar flare activity Authors: Ichimoto, K.; Kubota, J.; Suzuki, M.; Tohmura, I.; Kurokawa, H. Bibcode: 1985Natur.316..422I Altcode: The periodic nature of solar activity has been studied using parameters such as the sunspot Wolf numbers, calcium plage areas and flare indices. The magnitude of the solar activity based on these parameters reveals periodicities other than the most pronounced 11-yr one. Any absolute detection of periodicity in active phenomena would have fundamental significance for our understanding of solar activity. Here we investigate the temporal variation of the flare activity of the Sun using the data of 8,821 Hα flares which occurred during the period January 1965 to February 1984, and show new evidence for 155-day and 17-month periodicities of the flare activity. The 155-day periodicity is examined by taking into account the location of the flare on the Sun. It is suggested that the 155-day period may be related to the timescale for the storage and/or the escape of the magnetic field. Title: Hα Red Asymmetry of Solar Flares Authors: Ichimoto, K.; Kurokawa, H. Bibcode: 1984SoPh...93..105I Altcode: The evolutional characteristics of the red asymmetry of Hα flare line profiles were studied by means of a quantitative analysis of Hα flare spectra obtained with the Domeless Solar Telescope at Hida Observatory. Red-shifted emission streaks of Hα line are found at the initial phase of almost all flares which occur near the disk center, and are considered to be substantial features of the red asymmetry. It is found that a downward motion in the flare chromospheric region is the cause of the red-shifted emission streak. The downward motion abruptly increases at the onset of a flare, attains its maximum velocity of about 40 to 100 km s-1 shortly before the impulsive peak of the microwave burst, and rapidly decreases before the intensity of Hα line reaches its maximum. Referring to the numerical simulations made by Livshits et al. (1981) and Somov et al. (1982), we conclude that the conspicuous red-asymmetry or the red-shifted emission streak of Hα line is due to the downward motion of the compressed chromospheric flare region produced by the impulsive heating by energetic electron beam or thermal conduction. Title: Solar active regions and flares. Authors: Kurokawa, H. Bibcode: 1984AstHe..77..136K Altcode: No abstract at ADS Title: A CMG attitude control system for balloon use Authors: Kurokawa, H.; Yajima, N.; Usui, S. Bibcode: 1984spte.symp.1211K Altcode: A plan for a balloon-borne platform for astronomical observation and its control system is derived. For a control torquer, single-gimbal control moment gyros (CMGs) with a pyramid configuration were chosen. A new steering law is presented with its computer simulation results for such CMGs. Title: The Height of Hα Flare Emitting Region Authors: Kurokawa, Hiroki Bibcode: 1983SoPh...86..195K Altcode: No abstract at ADS Title: Observations of a compact solar flare on 1981 September 7 in Hα, X-ray, and microwave radiations Authors: Kanno, Mitsuo; Kurokawa, Hiroki; Hinotori Group Bibcode: 1983SoPh...86..193K Altcode: No abstract at ADS Title: Morphological and Evolutional Features of Ellerman Bombs Authors: Kurokawa, H.; Kawaguchi, I.; Funakoshi, Y.; Nakai, Y. Bibcode: 1982SoPh...79...77K Altcode: Morphological and evolutional features of Ellerman bombs were studied with Hα filtergrams of two active regions very close to the solar limb. We quantitatively determined the elongated or spike-like shape of the bomb. The mean apparent length of 174 bombs is 1.1 arc sec, while 80% of 204 bombs have a diameter of less than 0.6 arc sec. The mean lifetime of 77 bombs is about 12 min at Hα - 1.2 Å. The first maximum brightness of a typical bomb is attained, on average in about 2 min. Bombs grow longer in the first brightening phase and their mean upward velocity explains the blue asymmetry of Hα emission profiles of moustaches. Title: Progressive Brightenings Observed in the Wing of Hα Line Authors: Kawaguchi, I.; Kurokawa, H.; Funakoshi, Y.; Nakai, Y. Bibcode: 1982SoPh...78..101K Altcode: In an active region, several points were observed to brighten progressively on the monochromatic image of Hα - 1.2 Å formed by the Domeless Solar Telescope installed recently at Hida Observatory. The phenomena were interpreted as small flares or subflares. The propagation velocity was measured in two cases and discussed in terms of the multiple loop activation observed in EUV radiation. Title: Hα Fine Structures in the 1981SEP7 Flare and Their Relation to X-Ray and Microwave Emission Authors: Kurokawa, H.; Kanno, M. Bibcode: 1982sofl.symp..199K Altcode: No abstract at ADS Title: Heterogeneous structures of the lower corona. Authors: Saito, S.; Kurokawa, H.; Ogimachi, Y. Bibcode: 1981otse.conf...31S Altcode: No abstract at ADS Title: Some Observational Results on Ellerman Bomb Authors: Kurokawa, H. Bibcode: 1980jfss.conf..206K Altcode: No abstract at ADS Title: The Coronal Condensation Observed at the 1973 Eclipse Authors: Kurokawa, H. Bibcode: 1975SoPh...43..385K Altcode: The flash spectrograms obtained at the June 30, 1973 eclipse contain the monochromatic images of a coronal condensation in three coronal lines of FeXIV 5303, FeX 6374 and FeXI 7892 and Hα line. The assumption of the axially-symmetric distribution of the emissivity in the coronal lines allows us to find the density and temperature structure of the coronal condensation. While the electron density in the central axis of the condensation is about ten times as high as that of the normal corona at each height, the temperature is not so high (T⩽2.3×106K). This seems to be a representative nature of a coronal active region in the post maximum phase of activity. It is found that there exists a cool and dense core (T = 106K, Ne=6 × 109 cm-3 at 17000 km) at the lower part of the coronal condensation, which is in a close geometrical coincidence with the small active prominence protruding from the underlying plage region. Title: Observations of the total solar eclipse of 7 March, 1970. Authors: Kanno, M.; Tsubaki, T.; Kurokawa, H. Bibcode: 1974MmKyo..34..281K Altcode: 1974KyoMe..34..281K No abstract at ADS Title: The Continuum of the Extreme Limb and the Chromosphere at the 1970 Eclipse Authors: Kurokawa, H.; Nakayama, K.; Tsubaki, T.; Kanno, M. Bibcode: 1974SoPh...36...69K Altcode: The flash spectra of the partial Sun and the chromosphere were obtained at the total solar eclipse on 7 March, 1970. We studied the distributions of the surface brightness of the continuum at six wavelengths in the visual region to compare them with the previous observations and the existing model atmospheres. All of the distributions show a shallow dip and a small hump similar to those of Heintze's observation at the 1954 eclipse. But the hump in our results is of quite a different type from that given by Heintze's revised model. It was found that none of the existing model atmospheres can reproduce this hump. The intensity distribution in the low chromosphere was also examined. Title: A large flare of August 2, 1972. Authors: Kubota, J.; Kurokawa, H.; Kureizumi, T. Bibcode: 1972RISRJ..26..288K Altcode: No abstract at ADS Title: Fine Structure in the Inner Corona Observed at the 1970 Eclipse (Papers presented at the Proceedings of the International Symposium on the 1970 Solar Eclipse, held in Seattle, U. S. A. , 18-21 June, 1971.) Authors: Tsubaki, T.; Kurokawa, H.; Kanno, M. Bibcode: 1971SoPh...21..305T Altcode: On the slit spectrogram obtained at the 1970 eclipse in Mexico, the intensities of four coronal lines (NiXIII λ5116, FeXIV λ5303, FeX λ6374, and NiXV λ6702) and the continuum were measured as a function of distance along the slit. It is found that there exist a lot of fine fluctuations both in the lines and in the continuum intensities superposed on a large scale formation. The correspondence of such fluctuations between the continuum and the lines is good, with the exception of the line λ6374 which shows a peculiar fluctuation. It is shown that the intensities of the three lines λλ5116, 5303, and 6702 seem to be proportional to the square of the continuum intensity while the λ6374 line intensity may be proportional to the fourth power or more. Title: On the Coronal Lines in the Chromosphere at the 1970 Eclipse (Papers presented at the Proceedings of the International Symposium on the 1970 Solar Eclipse, held in Seattle, U. S. A. , 18-21 June, 1971.) Authors: Kanno, M.; Tsubaki, T.; Kurokawa, H. Bibcode: 1971SoPh...21..314K Altcode: Spectrographic observations of the flash spectrum were made by the Kwasan Observatory at the total solar eclipse on 7 March, 1970. The integrated intensities of FeXIV λ5303, FeX λ6374, and the continuum were measured on the spectrograms as a function of height above the Sun's limb. It was found that a large amount of emission in the coronal lines originates in the interspicular regions of the chromosphere. Analysis of the data yielded that the interspicular regions consist of coronal material of Te = 1.6 × 106-1.2 × 106 and log Ne = 8.5-9.5, and that a decrease in Te and an increase in Ne occur with decreasing height. Title: The Flash Spectrum Observed at the Total Eclipse of February 5, 1962 Authors: Kurokawa, H.; Tominaga, S.; Kubota, J.; Kawaguchi, I. Bibcode: 1969PASJ...21..141K Altcode: At the total solar eclipse of February 5, 1962, the flash spectrum was observed at Lae, New Guinea. Logarithmic intensities of about 130 emission lines were obtained at several positions on the east and west limbs of the sun in the wavelength range from 5850 A to 6563 A. A comparison of our intensities with those previously published is made. Two types of abnormal intensity gradients of the Ha and D3 lines were found in the active region very near the west limb and the observed spectral features are described in some detail. A comparison between the flash spectrograms and the whitelight or the monochromatic images of the solar disk before the eclipse reveals that the emission line intensities of Ha and D3 extend to large altitudes in the chromosphere over the active region ex9ept in the close vicinities of the sunspot where the intensities decrease rapidly.